 
Tree Care Kit:

Damage Prevention and Disaster Recovery

By Ecosystem Science and Management Extension Unit,  
Texas AgriLife Extension Service,  
Texas A&M University System

Copyright 2012 Texas AgriLife Extension Service

Smashwords Edition

Smashwords Edition, License Notes

Thank you for downloading this free ebook. Although, this is a free ebook, it remains copyrighted property of The Texas AgriLife Extension Service, The Texas A&M University System, and may not be reproduced, copied or distributed for commercial purposes.

Table of Contents

Tree Care Kit: Damage Prevention and Disaster Recovery

Introduction to Tree Care:

How Trees Grow

Benefits of Trees

Owners Rights & Responsibilities

Tree Identification and Selection:

Tree Identification

Environmental Factors to Consider

Poorly Drained Soils: What Should I Do

Shade Tolerance of Trees

Flood Tolerance of Trees

Drought Tolerant Trees

Planting and Tree Maintenance:

Why Hire an Arborist

Right Tree Right Place

How To Plant A Tree

Watering Trees

Mulching Your Trees

How To Prune A Tree

Pruning Young Trees

Harmful Pruning Practices

Tree Support Systems

Post-Planting Tree Care

Replanting After A Storm

Tree Damage and Hazard Assessment:

Predicting Tree Failure

Tree Wounds

Prevention Of Tree Failure

Understanding Lightning And Associated Tree Damage

How To Recognize And Prevent Tree Hazards

The Texas Extension Disaster Education Network (EDEN) Website

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About Texas EDEN

Tree Care Kit: Damage Prevention and Disaster Recovery

Texas has experienced increased homeownership in the last decade. Currently, more than 64% of all Texans own a home. This equates to approximately 14.6 million homes (total population = 22.9 million) and yards for which most have at least one tree. In fact, the average tree density within tree covered urban areas is approximately 204 trees per acre of tree cover. Homes in xeric urban environments are not excluded. Homeowners love their trees. Yet these trees are seldom properly maintained, and little thought is given to tree care and maintenance until catastrophic events occur and millions of dollars are loss as a result.

A large number of environmental stressors affect trees in Texas to some degree. Major weather events, perhaps the greatest stressors, have increased over the last decade due to changing climatic patterns. For example, seven category-three and above hurricanes occurred from 2001 through 2005 while only four category-three hurricanes occurred during the previous decade. Experts predict that this trend will continue for a number of years. It is reasonable then to anticipate frequent, hurricanes and severe storms during the next decade. Drought conditions have also taken their toll over the last seven years and will continue to do so. Ice storms also regularly cause major damage to Texas trees. Air pollution and other environmental factors, although not as perceptible, are significant. For example, Houston, Dallas, and Ft. Worth had 32, 26, and 23 ozone action days in 2006, respectively.

In order to prepare for these disasters, Texas AgriLife Extension Service needs to take a preemptive stand now and offer proper urban tree care outreach opportunities. Such opportunities will improve urban tree health, position urban trees to better withstand severe weather (hurricane, ice storms, drought), and minimize damage and loss of not only the beloved trees, but also surrounding structures (homes, vehicles, power lines, etc.) Homeowners will also be better informed about the best practices to follow to minimize hazard and loss from damaged trees.

Funded by a grant awarded through the Renewable Resources Extension Act, the objectives of this kit are:

1. Improve county Extension agents', and other tree care specialists', knowledge about urban tree care, damage prevention, and disaster recovery topics,

2. Provide this group with a kit containing all necessary information to conduct outreach programs and to evaluate tree damage in their county/area,

3. Instruct this group how to use the kit to conduct outreach programs and to evaluate tree damage in their county/area,

4. Reach a larger percentage of agents and other tree care specialists through distance educational efforts than would be possible through a single workshop,

5. Increase homeowner awareness of preventative maintenance and recovery, and ultimately reduce loss of trees and damage to surrounding structures.

6. Make these modules available to the Texas AgriLife Extension Service's Emergency Response initiative.

If you have questions or would like to receive additional information about this site, please contact  Dr. Melanie R. Kirk or  Dr. Eric Taylor.

Introduction to Tree Care

How Trees Grow

Mary L. Duryea and Marlene M. Malavasi  
School of Forest Resources and Conservation, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida

WHAT IS TREE GROWTH? Trees have six organs: leaves, stems and roots (vegetative structures) and flowers, fruits, and seeds (reproductive structures). Tree growth is the increase in size and numbers of the vegetative structures. Trees use the sun, carbon dioxide, water, and minerals to produce sugars. Sugars are the building blocks of tree growth. As a result, tree growth is as much a response to the environment as it is to the trees genetic make-up.

WHERE DOES GROWTH OCCUR? Growth occurs in meristems. A meristem is a tissue containing cells that have the capacity to divide to make new cells. In general, during growth cells divide, cells elongate, and cells differentiate into structures such as roots and shoots. Meristems can also produce new meristems called primordia. For example, an apical meristem in a bud produces new meristems called leaf primordial. Each leaf primordium will grow into a new leaf.

ABOVE GROUND GROWTH

Shoot Growth. Shoots elongate or grow in height at the tips of the branches. Apical meristems are located in the terminal buds at the tips of the branches. Cells at the apical meristem divide, elongate and differentiate in distinctly visible steps: (1) The bud at the tip of the branch opens, (2) Leaves emerge and enlarge, and (3) The area between the leaves expands (i.e., the stem grows). Lateral (side) buds grow in the same way but often these are dormant and do not grow until they are released after such activities as pruning.

Leaf Growth. On the surface of the apical meristem in the bud, a new meristem is formed. This new meristem is called a leaf primordium where cells divide and grow into a leaf. Soon after leaves develop, a new bud primordium (meristem) is formed at the base of each leaf stem. Once formed, this auxiliary bud has the capacity to become a branch, but may lie dormant for many years.

Diameter Growth. Between the wood and bark is a thin layer of dividing meristematic cells called the vascular cambium.

The cambium divides producing new wood towards the inside and bark on the outside. These new cells increase the diameter of the trunk and branches. The new wood cells, called xylem, carry water and minerals up from the roots to the leaves. The old wood in the middle is the heartwood. Heartwood, while dead, supports the weight of the tree. The inner bark cells, called phloem, carry sugars and other materials to the growth and storage locations of the tree.

New layers of wood are added each year between the bark and the previous year's wood. These are called growth or annual rings and may be used to age a tree. Annual rings vary in size and thickness according to the season that they are formed. Cells that are produced in the spring are larger with thinner cell walls. These are the light-colored rings, and the wood is called "early" or "spring" wood. Cells produced in the summer are smaller, and this "late" or "summer" wood has a higher density and darker color.

All woody trees have an outer bark that constantly renews itself and protects the tree from pest attacks and environmental impacts such as fire and mechanical injury. Some trees have thick bark that is resistant to injury. Others are easily injured because they have thin bark. As the tree grows in thickness, the outer part has to give, forming ridges and cracks in the bark. Eventually the outer bark sloughs off.

GROWTH BELOW GROUND. Roots can grow in length diameter, and number. At the tip of a root is the root cap. This cap protects the root and must be constantly replaced as a root pushes through the soil. Behind the root cap is a meristem which produces new cells for the root cap and for root elongation. These new cells elongate, divide and differentiate into root parts as it pushes through the soil.

Root diameter growth is similar to growth in the stem with the vascular cambium producing wood (xylem) and bark (phloem). A couple differences between root and shoot diameter growth are: (1) cambial growth is much more irregular in roots resulting in roots that are oval or irregular in cross section, and (2) there is greater variation in diameter with age and with horizontal roots compared to vertical roots.

Roots can also grow new lateral roots that form and branch off the main root. Some cells located in a layer inside the root produce a new root primordium. This new meristem divides and elongates pushing the root out through the parent root.

PHYSIOLOGICAL PROCESS. During the process of transpiration, water evaporates from the foliage through openings in leaves called stomata pulling adjoining water molecules with it. This pulling action helps draw water and nutrients up the trunk and into the leaves. In addition, some trees may be capable of exerting a pumping action to push water up the tree.

Photosynthesis, carried out in foliage, twigs and other green plant parts, produces sugars (and other components) that are used by the tree to carry out its many functions. Sugars, growth regulators, and proteins are moved about the plant in the phloem. Once sugar arrives at a location, it is used as energy for normal processes or it is stored as starch for later use. Trees need stored starch to carry out normal functions, especially to break dormancy in temperate trees.

LIFESPAN. Tree species have a wide range of lifespan. For example, while peach trees may live only 30 years, oaks may live 200 years, cypress 1,600 years, and bristle cone pine up to 5,000 years in an undisturbed site in the forest.

The average tree in urban settings, however, has only one tenth the lifespan of a tree at a rural site.

When a tree ages: (1) Growth slows down; (2) Trees are more susceptible to diseases and insects; (3) The tops of the trees are more likely to die back; (4) Wounds compartmentalize more slowly; (5) There are fewer numbers of leaves relative to the size of the tree; and (6) There is an increased number of dead branches. All of these characteristics can also be seen in urban trees as they begin to die and/or show signs of poor health.

REFERENCES

Bell, A.D. 1991. Plant Form: An Illustrated Guide to Flowering Plant Morphology. Oxford Univ. Press. New York. 341 pp.

Fahn, A. 1991. Plant Anatomy. Fourth edition. Pergamon Press. Oxford. 588 pp.

Harris, R.W. 1992. Integrated Management of Landscape Trees, Shrubs, and Vines. 2nd edition. Prentice-Hall. New Jersey. 674 pp.

Kozlowski, T.T., P.J. Kramer and S.G. Pallardy. 1991. The Physiological Ecology of Woody Plants. Academic Press. New York. 657 pp.

Laetsch, W.M. 1979. Plants - Basic Concepts in Botany. Little, Brown and Company. Boston. 510 pp.

Mosbrugger, V. 1990. The Tree Habit in Land Plants. In: S. Bhattacharji, G.M. Friedman, H.J. Neugebauer, and A. Seilacher (eds.). Lecture Notes in Earth Sciences , Vol. 28. Springer-Verlag. Berlin. 161 pp.

Wilson, B.F. The Growing Tree. 1984. Univ. Mass. Press. Amherst. 138 pp.

Benefits of Trees

International Society of Arboriculture

Most trees and shrubs in cities or communities are planted to provide beauty and shade. These are two excellent reasons for their use. Woody plants also serve many other purposes, and it often is helpful to consider these other functions when selecting a tree or a shrub for the landscape. The benefits of trees can be grouped into social, communal, environmental, and economic categories.

SOCIAL BENEFITS. We like trees around us because they make life more pleasant. Most of us respond to the presence of trees beyond simply observing their beauty. We feel serene, peaceful, restful, and tranquil in a grove of trees. We are "at home" there. The strong ties between people and trees are most evident in the resistance of community residents to removing trees to widen streets. Or we note the heroic efforts of individuals and organizations to save particularly large or historic trees in a community.

The stature, strength, and endurance of trees give them a cathedral-like quality. Because of their potential for long life, trees frequently are planted as living memorials. We often become personally attached to trees that we or those we love have planted.

COMMUNAL BENEFITS. Even though trees may be private property, their size often makes them part of the community as well. Because trees occupy considerable space, planning is required if both you and your neighbors are to benefit. With proper selection and maintenance, trees can enhance and function on one property without infringing on the rights and privileges of neighbors.

City trees often serve several architectural and engineering functions. They provide privacy, emphasize views, or screen out objectionable views. They reduce glare and reflection. They direct pedestrian traffic. They provide background to and soften, complement, or enhance architecture.

ENVIRONMENTAL BENEFITS. Trees alter the environment in which we live by moderating climate, improving air quality, conserving water, and harboring wildlife. Climate control is obtained by moderating the effects of sun, wind, and rain. Radiant energy from the sun is absorbed or deflected by leaves on deciduous trees in the summer and is only filtered by branches of deciduous trees in winter. We are cooler when we stand in the shade of trees and are not exposed to direct sunlight. In winter, we value the sun's radiant energy. Therefore, we should plant only small or deciduous trees on the south side of homes.

Wind speed and direction can be affected by trees. The more compact the foliage on the tree or group of trees, the greater the influence of the windbreak. The downward fall of rain, sleet, and hail is initially absorbed or deflected by trees, which provides some protection for people, pets, and buildings. Trees intercept water, store some of it, and reduce storm runoff and the possibility of flooding.

Dew and frost are less common under trees because less radiant energy is released from the soil in those areas at night.

Temperature in the vicinity of trees is cooler than that away from trees. The larger the tree, the greater the cooling. By using trees in the cities, we are able to moderate the heat-island effect caused by pavement and buildings in commercial areas.

Air quality can be improved through the use of trees, shrubs, and turf. Leaves filter the air we breathe by removing dust and other particulates. Rain then washes the pollutants to the ground. Leaves absorb carbon dioxide from the air to form carbohydrates that are used in the plant's structure and function. In this process, leaves also absorb other air pollutants such as ozone, carbon monoxide, and sulfur dioxide and give off oxygen.

By planting trees and shrubs, we return to a more natural, less artificial environment. Birds and other wildlife are attracted to the area. The natural cycles of plant growth, reproduction, and decomposition are again present, both above and below ground. Natural harmony is restored to the urban environment.

ECONOMIC BENEFITS. Individual trees and shrubs have value, but the variability of species, size, condition, and function makes determining their economic value difficult. The economic benefits of trees can be both direct and indirect. Direct economic benefits are usually associated with energy costs. Air-conditioning costs are lower in a tree-shaded home. Heating costs are reduced when a home has a windbreak. Trees increase in value from the time they are planted until they mature. Trees are a wise investment of funds because landscaped homes are more valuable than nonlandscaped homes. The savings in energy costs and the increase in property value directly benefit each homeowner.

The indirect economic benefits of trees are even greater. These benefits are available to the community or region. Lowered electricity bills are paid by customers when power companies are able to use less water in their cooling towers, build fewer new facilities to meet peak demands, use reduced amounts of fossil fuel in their furnaces, and use fewer measures to control air pollution. Communities also can save money if fewer facilities must be built to control storm water in the region. To the individual, these savings are small, but to the community, reductions in these expenses are often in the thousands of dollars.

TREES REQUIRE AN INVESTMENT. Trees provide numerous aesthetic and economic benefits but also incur some costs. You need to be aware that an investment is required for your trees to provide the benefits that you desire. The biggest cost of trees and shrubs occurs when they are purchased and planted. Initial care almost always includes some watering. Leaf, branch, and whole tree removal and disposal can be expensive.

To function well in the landscape, trees require maintenance. Much can be done by the informed homeowner. Corrective pruning and mulching gives trees a good start. Shade trees, however, quickly grow to a size that may require the services of a professional arborist. Arborists have the knowledge and equipment needed to prune, spray, fertilize, and otherwise maintain a large tree. Your county AgriLife Extension office, community forester, or consulting arborist can answer questions about tree maintenance, suggest treatments, or recommend qualified arborists.

THE PHC ALTERNATIVE. Maintaining mature landscapes is a complicated undertaking. You may wish to consider a professional plant health care (PHC) maintenance program that is now available from many landscape care companies. Their program is designed to maintain plant vigor and initially should include inspections to detect and treat any existing problems that could be damaging or fatal. Thereafter, regular inspections and preventive maintenance help ensure plant health and beauty.

Owners Rights & Responsibilities

American Forests, Arbor Day Foundation

Many of us own trees as part of our real estate. This endows us with certain rights associated with those trees. Tree ownership also requires certain duties on our part to prevent our trees from becoming a nuisance or a liability. The objective of this publication is to reduce misunderstandings among neighbors regarding their trees.

WHOSE TREE? How do we know whether it's our tree? It is your tree if you planted it or if a previous owner planted it and its main trunk is entirely within your property boundary. Naturally occurring trees are also generally the responsibility of the owner of the land on which they grow.

Boundary trees are those located on a common boundary line of adjoining landowners. Both landowners as tenants own these trees in common. Each landowner whose land contains any part of a tree trunk has an interest in that tree. Trees located completely on one person's property can be considered a boundary tree if the adjacent owners have treated it as common property by express agreement or by their course of conduct. Neither owner is at liberty to remove the tree without the consent of the other, nor to cut away the part that extends into his/her land, if injury would result in harm to the common property of the tree.

ADJOINING LANDOWNERS. Whether the tree is causing damage or not, if its branches extend beyond your property line, your neighbor has the right to trim your tree to the property line. Landownership rights extend indefinitely upward and down and those rights are protected from invasion by an adjoining landowner to the same extent as surface rights. In trimming the tree, your neighbor is not allowed to unduly harm your tree, however.

As a general rule, a landowner has no natural right to air, light or an unobstructed view. It has been held that such a right may be created by private parties through the granting of an easement or through the adoption of conditions, covenants and restrictions, or by the legislature by creating a right to sunlight for solar collectors or for satellite television. Local governments may impose restrictions that pertain to the property as to obstructions to air, light and view.

TREE OWNER RIGHTS. Our rights associated with trees limit nuisance claims and trespass with regard to cutting, trimming or removing trees that extend beyond property boundaries, especially abutting easements for streets and utility lines.

According to the trespass law, others are not allowed to harm our trees. Persons cutting, removing or otherwise harming our trees can be liable for double or triple the value of the tree if trespass is upheld. Typically, the most contentious "trespass" is tree trimming or right-of-way maintenance by utilities or municipalities.

In a tree-trimming dispute with a utility or service, first determine whether the company has the authority to trim or remove trees. Persons using a right-of-way generally have no rights unless granted by the jurisdiction's authority for proper use of the streets.

If authority exists, determine whether or not an easement is present on your property that would allow the public utility to enter the land. A landowner whose title extends to the center of the street has an interest in the trees adjacent to the public right-of- way. The authority of the utility to use the street does not empower or authorize it to damage the trees or otherwise appropriate any of the landowner's property without compensation. Contrast this situation to one where the municipality reserves the right to use your land for streets.

Generally, the easement holder has the right to remove obstructions located within the scope of the easement that threaten the full use of that easement.

The easement holder likewise has a duty to remove those obstructions in a way that causes the least destruction to the landowner's property. This is accomplished by doing only what is "reasonable and necessary" to insure the easement holder's full enjoyment of the easement. Reasonable and necessary are often subjective parameters and depend on the facts and circumstances of each case. Tree trimming standards do exist for most situations.

Many cases make it clear that a landowner's property interest in trees is subservient to a public utility company's right to remove and trim trees that interfere with the necessary and reasonable operation of the utility. The right of the general public to receive the benefits public utilities provide supersedes the rights of property owners to have trees located on their property untouched.

TREE OWNER'S RESPONSIBILITY. Generally, the landowner on whose property a tree grows will be held to a duty of care, determined by principles of negligence. Common prudence in tree maintenance is expected to prevent injury or damage to a neighbor's property.

A landowner with constructive or actual knowledge of a patently defective condition of a tree is liable for damages, injury or death caused by that tree. Tree owners in urban areas have a duty to inspect each and every tree on the premises to determine hazard trees and have them removed. In rural areas, there is no duty to inspect natural trees, but if you know or should have known hazardous trees exist, liability has held for natural trees in these areas.

Landowners are not typically liable for "Acts of God." An Act of God is an inevitable accident that could not have been prevented by human care, skill and foresight, but which results exclusively from nature's cause, such as lightning, storms and floods. A landowner will not escape liability for damages caused by an unsound or defective tree located on his/her property. It is not an Act of God if it could have been prevented by the exercise of reasonable diligence or ordinary care.

In short, a landowner will not be responsible for those injuries strictly arising out of an Act of God. If however, the injury could have been prevented by reasonable diligence or ordinary care or was an injury contributed to by human acts, the landowner will not be entitled to the Act of God defense and will be liable.

REFERENCES

Merullo, Victor D. and Michael J. Valentine. 1992. Arboriculture and the Law. International Society of Arboriculture Books, Savoy, IL.

Class notes. 2002. Trees, People and the Law Seminar, Tennessee State Cases and Statutes. May, 14, 2002. Nashville, TN

Pihlaja, Steve and Lorrie Stromme. 2002. In the Shade of a Tree; Analyzing the Tree-Related Legal Problem. Minnesota State Bar Association. Minneapolis. Bench and Bar of Minnesota, Volume 59(3). Online at: http://www2.mnbar.org/http://www2.mnbar.org/ benchandbar/2002/mar02/tree.htm

Tree Identification and Selection

Tree Identification

Eric L. Taylor, Melanie Kirk, and Chyrel Mayfield – Texas AgriLife Extension Service

INTRODUCTION. The first step in tree identification is knowing that there are distinguishing characteristics that separate one species or group from another. This fact sheet will provide some useful tools to make these distinctions. Several of these distinctions will be described in detail below.

HABITAT, SHAPE & COLOR. Some trees can be found growing on many different types of sites. Most trees, however, grow best on sites that satisfy their specific needs for moisture, light, soil, and biota (all the plant and animal life of a particular region). Other distinctions that can help in identification are shape and color. The shape and color of a tree can make identification possible even at a great distance. Some trees may change color in the fall while others my display a distinctive color or shape to help differentiate them from the next tree.

BARK & BRANCHING PATTERNS. Bark features can be very helpful in tree identification especially when leaves are absent and twigs inaccessible (Image 1). However, bark can vary greatly with age, growth rate and habitat. Key identifying features include: texture, color and color patterns, and color and size of variously shaped spots on young bark.

Branches, twigs, buds, and leaves grow at specific locations on the tree called nodes. Many species grow in an ALTERNATE pattern with one bud or leave per node (Image 2). Relatively few species have leaves or buds that occur in pairs at each node (OPPOSITE). Fewer species still grow with a WHORLED pattern with three or more structures at a node.

LEAVES. Leaves are often the easiest and most widely used way to identify a tree. There are many types of leaf traits that give clues in identifying trees. For example, leaf complexity offers very good clues to the species group. Individual leaves can be classified as either simple or compound (Image 3). Simple leaves have a single blade leaf. While compound leaves have two or more leaflets.

The direction in which the veins run along the blade also helps to identify the tree. Veins of a leaf are described as parallel, palmate, or pinnate (Image 4).

The shape of the leaf is very important in helping identify a particular tree (Image 5). Leaves can grow on conifers as either scales, single needles, or in groups called fascicles.

Leaf margins (edge of the leaf) are also key identifier as to the tree species (Image 6). The leaf margin can be: smooth (entire); uniformly sharp, finely toothed (serrulate); or maybe indented (lobed). Trees sometimes have much variability in their leaf shape. Your county AgriLife Extension office or local state forestry office are good sources of information for tree identification. In addition, a list of helpful resources is provided that may further assist in the tree identification process.

HELPFUL RESOURCES

1. National Audubon Society Field Guide to North American Trees By: Elbert Little

2. Tree Identification By George W. Symonds, George Wellington Dillingham Symonds

3. What Tree is That? http://www.arborday.org/ trees/whattree/?TrackingID=908

4. What Tree is It? http://www.oplin.org/tree

5. Rangeland Plants of Texas Database. http://essmextension.tamu.edu/plants

6. Trees of Texas http://texastreeid.tamu.edu

REFERENCES

Duncan, W.H., and Duncan, M.B., 1988. Trees of the Southeastern United States. The University of Georgia Press, Athens, Georgia 30602

Harlow, W.M., Harrar, E.S., Hardin, J.W. and White, F.M. 1996. Textbook of Dendrology. Eighth edition. McGraw-Hill. New York.

Nixon, E. S. 1985. Trees, Shrubs, & Woody Vines of East Texas

Forest Trees of Texas, How to Know Them... Bulletin 20, Texas Forest Service April, 1963 Eighth Edition, Ninth Printing, July 1993.

Environmental Factors to Consider

James R. Fazio Editor

When selecting a tree, your first consideration must be what the tree needs. In other words, what environmental factors limit the ability of a particular species to thrive in an area?

Temperature

Varying temperature ranges limit the geographic diversity of many species of trees. Low temperatures, especially if they come suddenly, can freeze and kill the living cells in trees not suited to colder climates. The same reaction can occur in many species that are not accustomed to high temperatures and drought conditions. Select a species suitable to the zone where you live. Remember, elevation and exposure differences (the direction of the slope) within each zone also have an effect. North slopes, windy sites and higher elevations can make a site equivalent to one or two hardiness zones lower.

Moisture

Each species can tolerate wet or dry growing conditions to a different degree. Special attention must be given to your selection if the site can flood, is subject to very dry conditions, or is continually exposed to the drying effect of wind. Watering, of course, can modify a dry site, but even when you irrigate it is important to know the optimal soil moisture requirements for your species. Light, sandy soils could be watered more frequently. Watering every day or every other day is way too much.

Light

Shade tolerance is the term foresters use to rate the light requirements of each species. Don't make the mistake of planting your tree where it is mismatched with its need for light.

Pests

Every locality has its problems with a particular insect or disease. The best way to avoid trouble is to avoid species that host these pests. In some cases, it is possible to buy varieties that have been bred for resistance to a disease.

Soil

Soil factors are probably the most overlooked when selecting a tree. Soil depth, structure and pH, in addition to soil moisture, can make the difference between success or failure after planting. Species that need light, sandy soil should not be planted in rocky or clay-type soils. Also, each tree species has a tolerance range related to acidity and alkalinity just as it does for shade. This requirement should be matched with the soil where you plan to plant. Soils are often disturbed in urban areas and trees which would typically do well may struggle due to poor soil structure. Compaction of the soil due to heavy pedestrian or vehicle use often reduces a tree's growth and size potential.

Air Pollution

Unfortunately, the ability of a species to tolerate air pollution is becoming more important. Chemicals in the air vary with localities, and in some cases the accumulative effects of pollution are just beginning to show up. The best course of action is to ask a local professional if there are problems in your town and, if so, what species are affected. Similarly, salt spray from either the ocean or street de-icing can be a problem locally and some species are more sensitive to it than others. Where these are problems, ask an arborist, nursery professional, urban forester, or AgriLife Extension agent about which trees to avoid.

Summary

In summary, it is important to analyze the various environmental factors in your area before selecting a tree. Temperature, moisture, light, pests, soil conditions, and air pollution will all affect your planting success.

References

Tree City USA Bulletin for the Friends of Tree City USA

Poorly Drained Soils: What Should I Do

Wayne K. Clatterbuck Assistant Professor Forestry, Wildlife & Fisheries University of Tennessee

Donna C. Fare Research Horticulturist USDA-ARS US National Arboretum

Preparation for planting is the key to success in establishing landscape plants. Site analysis and proper planting assure rapid plant establishment and healthy growth, provided environmental factors are favorable Investigate surface and internal water drainage in the landscape. Check for areas where water collects, drains slowly or stands for long periods. This fact sheet discusses the relationship between proper drainage and landscape trees.

Soil compaction and drainage

Many landscape plants die because they are planted in soil that is too wet or too dry. Soil with good porosity throughout the rooting depth allows large quantities of water to move through the soil profile without affecting plant roots unless there is a naturally high water table at the site. Typically, a soil contains about 50 percent solid materials and about 50 percent pore space, filled by air and water. In poorly drained soils, most of the pore space is filled with water for long periods of time, leaving too little air.

Many landscape sites do not have ideal drainage. During rainy weather, water may stand on the soil surface or drain very slowly. Consistently wet soils often have an odor caused by anaerobic bacteria in the soil.

Poor drainage can occur naturally. Bright soil colors indicate good water drainage, while a dull color or grayish tent could indicate poor drainage. Soils that are considered a challenge in landscape sites include:

- Somewhat poorly drained: Soil is wet for prolonged periods, but not all the time.

- Poorly drained: Soil remains wet for a large portion of the year.

- Very poorly drained: Soil remains wet year-round as the water table remains at or near the surface year-round.

Poor drainage often occurs when contractors remove topsoil during construction of new homes, leaving only subsoil. The amount of topsoil reapplied may be unknown. Also, during construction, heavy equipment may compact the soil reducing air space.

Poor drainage can also result from improper shaping of the yard, leading to ponding in low areas or around the foundation, or due to failure to properly remove runoff water from roofs, downspouts and streets.

Even if soil has not been removed or added during construction, the drainage patterns of unaltered native soils also may change. A hard pan may occur in areas that have had a lot of heavy equipment and traffic.

Corrective Action

An easy method to determine the drainage of a site is to dig a hole 12 inches long, 12 inches wide and 12 inches deep. Fill the hole with water. If the water drains in fewer than three hours, the drainage is excellent, and plants suited for dry locations will perform well. However, this method should be done only when the soil is moist. Poorly drained soils may drain excessively when the soil is dry giving the false impression of good drainage. Distributing large amounts of compost or organic material throughout the soil medium can greatly improve the water-holding capacity of the soil.

If the water takes from three to 12 hours to drain, then the drainage is adequate for most landscape plants (about 1 inch per hour). If it takes more than 12 hours, then the drainage is poor. But before corrective action is taken, dig a little deeper to see if there is an impermeable layer of soil that is restricting water movement. Although it is difficult to change the soil, you can alter the site to minimize the poor physical drainage. Check several locations in the landscape. Select trees that are tolerant of the wet conditions or change the site to meet the needs of the plants. In areas where it would be difficult to use equipment, dig a dry well to break through the hard pan. After the planting hole is dug, use a posthole digger to dig a hole about 12- 15 inches deep in the bottom of the planting hole. Fill this hole (dry well) with porous material, such as gravel. Then plant the ornamental tree. The dry well should allow the soil to drain below the hardpan layer. This method will only work properly if the well actually goes all the way through the restrictive layer. If it doesn't, the well will hold water like the rest of the planting hole.

Another way to handle a drainage problem is to raise the height of the soil. Elevate the site by adding 10-12 inches of well-drained topsoil, compost or other organic matter to raise the planting zone. The amendment should be tilled into the soil to provide a homogenous medium for the plants. The root zone of the tree is then adequately above any poor internal drainage. The addition of organic amendments should be addressed on a case-by-case basis.

Adding an organic amendment to an individual planting hole is not recommended. Extensive research has determined that organic amendments placed in the planting hole do not result in a larger root system or encourage root penetration into the native soil. Organic matter should be incorporated uniformly throughout the projected root zone, as opposed to putting it into the planting hole. At least a 1 percent increase in organic matter is required to have an effect on the water- and nutrient-holding capacity of a soil. Avoid using more than 50 percent organic matter, because plant problems may result from humic acids and other organic compounds. Apply the amendment uniformly over the existing soil that has been deep tilled (8-12 inches). Till or work the amendment in the soil until a homogenous mixture is developed.

Sometimes the problem can be solved by shaping the surface to allow runoff or by diverting excess water. Sometimes, the only way to overcome poorly drained soils is to install drain tile. In this extreme condition, make sure the drain tiles are installed to move soil water away from structures and ornamental trees. Drain tiles are an expensive technique to modify the planting area, but the results are typically worth the effort.

Summary

Soil conditions and drainage play a key role in the success or failure of trees in the landscape. It is important to analyze the site prior to planting and take corrective action to ensure the success of your trees.

Shade Tolerance of Trees

Wayne K. Clatterbuck Associate Professor Forestry, Wildlife & Fisheries University of Tennessee

Most trees have very specific requirements for how much sunlight or shade that they are able to endure. Some trees do well in full sunlight, while other trees do not perform as well. Recognizing the light requirements of different species of trees will assist in proper tree selection in the landscape and will promote healthy trees. This fact sheet discusses and lists the comparative tolerance of trees to shade or sunlight.

Shade tolerance is a comparative term used to describe a tree species' ability to become established, grow and persist under shade or low light intensity, quality and duration. Tolerant species can grow comparatively well when little light is available. Intolerant species cannot grow well in low light levels, but grow very well at light levels approaching full sunlight.

Knowledge of tolerance is necessary in establishing and managing trees in urban landscapes. Unfortunately, many shade-tolerant trees are planted in full sunlight conditions, increasing the stress and affecting their physiological processes. These trees usually do not adapt readily to increased light levels, usually decline and may eventually die. Shade-tolerant trees grow best in partial shade beneath larger trees or nearby structures or buildings that provide some shade during the day.

Sunlight is the key to successful flowering of trees. Enough sunlight must reach the tree for flowers and fruit to develop.. As the amount of sunlight decreases, so will the number of flowers. Thus, management of the amount of sunlight received by more shade-tolerant trees should be balanced to provide enough sunlight for flowering, but not so much that it affects the health of the tree.

Age affects tolerance, as trees usually become more intolerant with age. Most maples and oaks are more shade-tolerant when young, but become more intolerant as they mature. Tolerant species are usually photosynthetically more efficient because they are able to utilize light at lower levels than shade-intolerant trees.

The morphology and physiology of leaves and trees that are tolerant and intolerant of shade are quite different. These attributes of trees can provide different species with different shade tolerances.

Flood Tolerance of Trees

Wayne K. Clatterbuck Associate Professor Forestry, Wildlife & Fisheries University of Tennessee

Flood Tolerance

Trees have varying tolerances to flooding. However, flooding during the growing season, especially during and after leaf out, can be harmful to trees. The roots need oxygen to survive and grow. Flooding results in poor aeration, because the oxygen supply in flooded soil is severely limited. Oxygen deficiency is likely the most important environmental factor inhibiting growth and causing injury in flooded trees. Most trees will tolerate flowing water for a few days during the growing season. Flowing water retains dissolved oxygen (aerobic conditions) such that the oxygen to the roots is not depleted. However, oxygen is exhausted (anaerobic conditions) in water that is standing or puddled. Few trees can tolerate standing or puddled water during either the dormant or growing season.

Once trees are stressed by floods (symptoms are leaf yellowing, defoliation, reduced leaf size, sprouting and crown dieback), secondary organisms, particularly opportunistic fungi, insects and disease, invade the hosts and further weaken the tree. These symptoms may progress and eventually lead to tree death, especially with repeated, annual flooding. Generally, though, flooding does not occur each year and stress symptoms may subside, indicating the tree is recovering.

Summary

Knowledge of the varying tolerances of different tree species to flooding is critical in selecting the right tree for the right place for planting and for managing growth and development of trees in the landscape. Trees that are not well suited to certain moisture conditions will perform poorly. Matching the tree's physiological requirements to its most conducive environment will increase the probability of success in managing your landscape with minimum maintenance costs.

References

Bratkovich, S., L. Burban, S. Katovich, C. Locey, J. Pokorny, and R. Wiest. 1994. Flooding and its effects on trees. Miscellaneous Information Packet. St. Paul, MN: U.S. Department of Agriculture, Forest Service, State and Private Forestry, Northeastern Area (http://www.na.fs.fed. us/spfo/pubs/n_resource/flood/cover.htm)

Burns, R.M. and B.H. Honkala. 1990. Silvics of North America (2 volumes). Agricultural Handbook 654. Washington, DC: U.S. Department of Agriculture, Forest Service.

Daniel, W.W., J.A. Helms and F.S. Baker. 1979. Principles of Silviculture. McGraw Hill, Inc. New York. 500 p.

Gilman, E.F. and D.G. Watson. 1993. Tree selection for landscapes. Fact Sheets. Gainesville, FL: University of Florida, Institute of Food and Agricultural Sciences, Department of Environmental Horticulture (www.hortifas.ufl.edu/trees/)

Johnson, P.S. 1989. Principles of natural regeneration. Publication 3.01 in Central Hardwood Notes (F.B. Clark and J.G. Hutchinson, eds.). St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station. 5 p.

Smith, D.M., B.C. Larson, M.J. Kelty and P.M.S. Ashton. 1997. The Practice of Silviculture: Applied Forest Ecology. Ninth Edition. John Wiley & Sons, Inc. New York. 537 p.

Whitlow, T.H. and R.W. Harris. 1979. Flood tolerance in plants: a state-of-the-art review. Technical Report E-79-2. Vicksburg, MS: U.S. Army Engineer Waterways Experiment Station. 161 p.

Drought Tolerant Trees

Wayne K. Clatterbuck Associate Professor Forestry, Wildlife & Fisheries University of Tennessee
Introduction

Late-season droughts are common in many Texas landscapes. Many trees are stressed by prolonged periods of hot, dry weather. Selecting trees that use water efficiently without the need for frequent watering or irrigation is one way to make your landscape more resistant to droughts. With impending water shortages in many urban areas leading to prohibitions of irrigation or watering, planting trees that are more tolerant to drought conditions is the best long-term solution to a healthier, low-maintenance landscape.

Thick leaf waxes of Eastern red cedar foliage assist in its drought tolerance.

A few of the factors to consider when selecting trees that use water efficiently are:

\- Native trees are better adapted to local soil, moisture, climate and pest conditions than non-native trees.

\- Trees with small leaves are more easily cooled and have better water-use efficiency than trees with larger leaves.

\- Upland species are usually more drought-resistant than bottomland species.

\- Early successional species, those that colonize old fields and disturbed sites, use water more effectively than late successional species.

\- Trees with deep, upright crowns are more effective in water use than those with flat, wide-spreading crowns.

\- Trees with multilayered crowns having many living branches and leaf layers are more water-efficient than those trees with leaf canopies that concentrate leaves in single layers along the outer edge of the crown.

\- Drought-tolerant plants usually have thick leaf waxes and bark, efficient stomatal control, and extensive root systems.

Although there is not an ideal drought-resistant tree for every landscape, many trees have drought-resistant features and are more tolerant of dry conditions than others. For more information on selecting a tree, check the Texas Forest Service tree-planting guide at http://texastreeplanting.tamu.edu. However, as with any new planting, they will need to be watered until they are established.

References

Coder, Kim D. 1999. Tree selection for drought resistance. The University of Georgia, Warnell School of Forest Resources, Athens GA. 4 p

Planting and Tree Maintenance

Why Hire an Arborist

International Society of Arboriculture

An arborist is a specialist in the care of individual trees. Arborists are knowledgeable about the needs of trees and are trained and equipped to provide proper care. Hiring an arborist is a decision that should not be taken lightly. Proper tree care is an investment that can lead to substantial returns. Well-cared-for trees are attractive and can add considerable value to your property. Poorly maintained trees can be a significant liability. Pruning or removing trees, especially large trees, can be dangerous work. Tree work should be done only by those trained and equipped to work safely in trees.

Service that Arborists Can Provide:

Pruning

An arborist can determine the type of pruning necessary to maintain or improve the health, appearance, and safety of trees.

These techniques include:

\- eliminating branches that rub each other

\- removing limbs that interfere with wires, building facades, gutters, roofs, chimneys, or windows, or that obstruct streets or sidewalks

\- removing dead or weak limbs that pose a hazard or may lead to decay

\- removing diseased or insect-infested limbs

\- creating better structure to lessen wind resistance and reduce the potential for storm damage

\- training young trees

\- removing limbs damaged by adverse weather conditions

\- removing branches, or thinning, to increase light penetration

\- improving the shape or silhouette of the tree

Removal

Although tree removal is a last resort, there are circumstances when it is necessary. An arborist can help decide whether a tree should be removed. Arborists have the skills and equipment to safely and efficiently remove trees. Removal is recommended when the tree:

\- is dead or dying

\- is considered irreparably hazardous

\- is causing an obstruction that is impossible to correct through pruning

\- is crowding and causing harm to other trees

\- is to be replaced by a more suitable specimen

\- is located in an area where new construction requires removal

Emergency Care

Storms may cause limbs or entire trees to fall, often landing on other trees, homes and other structures, or cars. The weight of storm-damaged trees is great, and they can be dangerous to remove or trim. An arborist can assist in performing the job in a safe manner, while reducing further risk of damage to property.

Planting

Many arborists also provide a variety of other tree care services, including Plant Health Care (PHC). This concept of preventive maintenance keeps trees in good health, which will help the tree better defend itself against insects, disease, and site problems.

PHC includes:

\- fertilization

\- cabling or bracing for added support to branches with weak attachment

\- aeration to improve root growth

\- installation of lightning protection systems

\- spraying or injecting to control certain insect and disease problems.

Selecting the Right Arborist for the Job

When selecting an arborist:

\- Check for membership in professional organizations such as the International Society of Arboriculture (ISA), the Tree Care Industry Association (TCIA), or the American Society of Consulting Arborists (ASCA).

\- Check for ISA arborist certification.

\- Ask for proof of insurance and then phone the insurance company if you are not satisfied. A reputable arborist carries personal and property damage insurance as well as workers compensation insurance.

\- Check for necessary permits and licenses. Some governmental agencies require contractors to apply for permits and/or to apply for a license before they are able to work.

\- Ask for references to find out where the company has done work similar to the work you are requesting.

\- Get more than one estimate, unless you know and are comfortable with the arborist. You may have to pay for the estimates, and it will take more time, but it will be worth the investment.

\- Don't always accept the low bid. You should examine the credentials and the written specifications of the firms that submitted bids and determine the best combination of price, work to be done, skill, and professionalism to protect your substantial investment.

\- Be wary of individuals who go door to door and offer bargains for performing tree work. Most reputable companies are too busy to solicit work in this manner. Improper tree care can take many years to correct itself and, in some cases, it can never be corrected. Are you willing to take that risk with your valuable investment?

\- Keep in mind that good arborists will perform only accepted practices.

\- Get it in writing. Most reputable arborists have their clients sign a contract. Be sure to read the contract carefully. Don't be afraid to ask questions, such as:

\- - When will the work be started and completed?

\- - Who will be responsible for clean-up?

\- - Is this the total price?

\- - If I would like more to be done, what is your hourly rate?

Be an informed Consumer!

One of the best methods to use in choosing an arborist is to educate yourself on some of the basic principles of tree care. ISA offers several other brochures in this series, which discuss many of the basic principles of tree care. Your local garden center, extension agent, or city arborists are also excellent sources of information if you should have further questions. They may also be able to refer you to an ISA Certified Arborist in your area.

Right Tree Right Place

Donna C. Fare and Wayne K. Clatterbuck University of Tennessee

Trees enhance the beauty and value of homes, streets and communities. However, trees planted in the wrong place can cause property damage and become a detriment rather than an asset. Carefully planning the location and species of a tree will ensure that the tree will be an asset and not grow into a hazard or a nuisance. Before choosing a tree, consider these factors:

\- Purpose for planting the tree,  
\- Soil conditions,  
\- Tree location (the right place),  
\- Species growth and form (the right tree), and  
\- Undesirable species traits.

Purpose for Planting a Tree

Trees provide many benefits for the home landscape. Shade, color, vertical dimension, soundproofing, cooling, beauty, screening, windbreaks, boundary lines and wildlife habitat are just a few. Tree use is varied: framing the view of a house or landscape, screening out eyesores, dividing the landscape area, creating privacy and conserving energy. Landscape trees can be shade trees, flowering trees, framing trees, border trees, street trees, patio trees, fruit or nut trees and wildlife trees. Trees may also enhance property values. Once the purpose of the planted tree is determined, then other factors should be used to select the right tree.

Soil Conditions

Most trees grow best in a moist, deep, fertile, well-drained soil. Unfortunately, these soils do not occur frequently on developed property in urban areas. Soil conditions are probably the most overlooked factor when selecting a tree. Both the physical and chemical properties of soils in developed areas have usually been altered which affects fertility, aeration and drainage. Choosing trees that are best suited for the soil conditions on your property will govern how well they grow and prosper.

Soil fertility can easily be judged with a soil test. Soil tests will give indications of available nutrients, soil pH, and organic matter content. Contact your county AgriLife Extension office for soil testing information.

The physical aspects of the soil include its volume and texture (amount of sand, silt and clay). These soil properties influence aeration, internal drainage and water-holding capacity. The optimum soil for tree growth has a loamy texture (mixture of sand, silt and clay). Some tree species can better tolerate clay soils; others are more suited to sandy soils. Compaction of the soil decreases pore space and stresses the tree by reducing the amount of oxygen to the roots.

Tree Location – The Right Place

Growing space both above and below ground should be considered when selecting a tree to plant. Too often allowances are not made for the increased size of the tree when it matures. Some of the problems that can be avoided by selecting the proper tree for the available planting space are:

\- Damage to houses through cracked foundations, leaves in gutters or abrasion of tree limbs hitting the house;

\- Cracked pavement of sidewalks, driveways, porches and patios;

\- Sewer lines or septic tanks clogged by roots;

\- Dangerous screening by obscuring traffic signs, pedestrians or vehicles;

\- Storm damage and electrical problems from trees or limbs affecting utility lines; and

\- Blocking scenic views or windows.

One objective for planting trees in a residential setting is to provide shade to cool homes during the summer months. For morning shade, plant trees on the southeast exposure of the house. For afternoon shade, trees should be planted on the southwest exposure. Deciduous trees (those that lose leaves during the winter) allow the sun to warm the house during winter and shade it during the summer months. Evergreen trees planted on a northern exposure will screen or block cold winter winds.

Remember that trees will become larger with age. Your evaluation of the site before planting will allow you to choose the correct size of tree for the site, avoid crowding before it occurs and save time and money at some future date.

Species Growth and Form – The Right Tree

Once the soil and site conditions for tree planting are determined and evaluated, then homeowners can factor in their personal preferences when choosing a species of tree. Characteristics such as tree shape, size, flowering, colors and texture should be considered. Trees must be selected carefully in order to accomplish their intended purpose satisfactorily, and to continue to do so with future growth and development.

Tree Shape and Form

Different species of trees have different crown forms, such as round, oval, weeping, and pyramid, columnar or spreading. Selection of a proper form will satisfy your landscape objectives, enhance your property and decrease future maintenance costs. Trees with low-spreading branches are suitable for screens, but not for placement along driveways where visibility is essential. Columnar or upright trees are appropriate for medians and property boundaries, but not for providing shade for a house.

Tree Size, Growth and Longevity

Always plan for the growth and future size of a tree. The small trees planted today may be the large trees of tomorrow. Evaluate the mature height and spread of the tree, as well as its lifespan. Some trees grow and provide shade quickly within 30 years, then decline and eventually die. However, the growth rate and size of the tree may be acceptable as a yard tree during its first 50 years for shade and enjoyment. Thus, consideration should be given to whether the tree is planted for posterity or to fulfill an immediate need that may have future consequences.

Sunlight

Some trees are more adapted to certain intensities and amounts of light than others. Shade tolerance is a term used to rate the capacity of a tree to develop and grow in the shade of other trees.

Undesirable Species Traits

Most trees will have some undesirable traits that may be considered obnoxious by some and tolerated by others. Most of the unfavorable traits are associated with insects and disease, production of fruits and seeds and tree maintenance.

Insects and Disease

Trees are susceptible to many insects and diseases. Most of these problems are species-specific and should be considered when selecting a tree to plant. Consult with your local garden center, nursery, tree care professional, county AgriLife Extension office or forester to discuss if a tree being selected is prone or sensitive to local diseases or insects.

Fruits and Seeds

Some fruits and seeds are nuisances to property owners, but may be valued by others. If the homeowner is interested in providing food for wildlife, fruits and seeds will attract many birds and animals. However, some seed can annoy landowners.

Maintenance

Tree maintenance is an unavoidable task that homeowners should include in their evaluation of a tree. Most fast-growing trees will require more frequent maintenance than species with moderate to slow growth. The weak wood of many fast-growing trees requires heavy cleanup of limbs and debris after storms and may disrupt utility service and highway traffic.

Summary

Once the tree is selected, purchased and planted, considerable costs have already been incurred. If the tree is not suited for the growing space or location, it may not survive, resulting in a loss of time and money. If the tree survives, but was poorly selected, the homeowner or community will have considerable expenses for its care. The right tree in the right place will provide benefits for many years with minimum costs.

How To Plant A Tree

American Forests, Arbor Day Foundation

Giving your trees the right care from day one is essential for long life and health. This means taking the time and care to plant a tree properly.

When to Plant Trees

Climate plays a deciding role when determining the appropriate planting time. Newly planted trees do best when exposed to moderate temperature and rainfall and they need time to root and acclimatize before the onset of intense heat and dryness of summer or the freezing temperatures of winter. Spring and fall, therefore, are generally the best planting seasons. In the southern United States, however, which do not experience an intense winter, planting can take place during the winter months.

A schematic illustrating the strategic location of trees around a home to conserve the amount of energy required to heat and cool a home.

Where to Plant Trees

Planting trees strategically around your home will conserve energy and lower the cost of utility bills. Three well-placed deciduous trees on the east, south, and west sides of a home will shade it from summer sun and lower cooling costs by 10 to 50 percent.

Trees can also produce savings in cold weather. Staggered rows of evergreen trees on the northwest side of the house (or the side with prevailing winter winds) will block harsh winds and lower heating costs.

How to Plant a Tree

To get started, first choose at least a five to six-foot tree grown to nursery standards that is an appropriate species for the site (see fact sheet 1.4). Then select a site with enough room for roots and branches to reach full size. Make sure to avoid overhead and underground utilities.

The Hole

While planting different types of trees differs in the details, all trees eventually end up in a hole. But not any old hole will do. The most common mistake when planting a tree is a digging hole, which is both too deep and too narrow. If the hole is too deep, the roots have insufficient oxygen to ensure proper growth. If the hole is too narrow, the roots cannot expand to nourish and properly anchor the tree.

As a general rule, trees should be transplanted no deeper than the soil in which they were originally grown. The width of the hole should be at least 3 times the diameter of the root ball or container or the spread of the roots in the case of bare root trees. This will provide the tree with enough worked earth for its root structure to establish itself.

When digging in poorly drained clay soil, it is important to avoid 'glazing.' Glazing occurs when the sides and bottom of a hole become smoothed forming a barrier, through which water has difficulty passing. To break up the glaze, use a fork to work the bottom and drag the points along the sides of the completed hole. Also, raise the bottom of the hole slightly higher than the surrounding area. This allows water to disperse, reducing the possibility of water pooling in the planting zone.

Balled and Burlapped Trees (B&B)

B&B trees, although best planted as soon as possible, can be stored for some time after purchase as long as the ball is kept moist and the tree stored in a shady area. B&B trees should always be lifted by the ball, never by the trunk. The burlap surrounding the ball of earth and roots should either be cut away completely (mandatory, in the case of synthetic or plastic burlap) or at least pulled back from the top third of the ball (in the case of natural burlap). Any string or twine should also be removed. Backfill soil (combinations of peat moss, composted manure, topsoil, etc.) is then placed in the hole surrounding the tree just to the height of the ball or slightly lower to allow for some settling. Be careful not to compress the back fill soil as this may prevent the roots from expanding beyond the ball.

Container Trees

Container trees are subject to greater heat and drying conditions than B & B. They can only be stored for a brief period of time after purchase as long as the soil in the container is kept moist and the tree stored in a shady spot. The procedure for planting container trees is similar to that for B&B trees. In the case of metal or plastic containers, remove the container completely. In the case of fiber containers, tear the sides away.

Once carefully removed from the container, check the roots. If they are tightly compressed or 'potbound', use your fingers or a blunt instrument (to minimize root tearing) to carefully tease the fine roots away from the tight mass and then spread the roots prior to planting. In the case of extremely woody compacted roots, it may be necessary to use a spade to open up the bottom half of the root system. The root system is then pulled apart prior to planting. Loosening the root structure in this way is extremely important in the case of container plants. Failure to do so may result in the roots 'girdling' and killing the tree. To further assist this, lightly break up even the soil outside the planting zone. This allows roots that quickly move out of the planting zone to be more resilient as they anchor into existing surrounding soil conditions.

Once the tree is seated in the hole, the original soil is then back-filled into the hole to the soil level of the container. Again, remember not to overly compress the back-filled soil especially by tramping it with your feet. Compress gently using your hands instead.

Bare-Rooted Trees

Planting bare-rooted trees is a little different as there is no soil surrounding the roots. Most importantly, the time between purchase and planting is a more critical issue. Plant as soon as possible. When purchasing bare-rooted trees, inspect the roots to ensure that they are moist and have numerous lengths of fine root hairs (healthy). Care should be taken to ensure that the roots are kept moist in the period between purchase and planting. Do NOT prune the roots.

To plant, first build a cone of earth in the centre of the hole around which to splay the roots. Make sure that when properly seated on this cone the tree is planted so that the 'trunk flare' is clearly visible and the 'crown', where the roots and top meet, is about two inches above the soil level.

Fertilizers and Other Soil Amendments

After you plant your tree, there are certain products that can be added to the soil to help the roots establish themselves. A root-promoting fertilizer can help, but ensure that the fertilizer is not simply placed in the planting hole. Fertilize the soil around the planting hole as well to promote root expansion.

Finishing the Job

\- Remove tags and labels.

\- Do not stake the trunk unless the tree has a large crown, or the planting is situated on a windy site or where people may push them over. Stake for a maximum of one year. NOTE: Evergreens rarely require staking.

\- Soak soil well, making sure no air pockets form between roots.

\- Add 2″ – 3″ of mulch, taking care to keep it away from the trunk.

\- Prune basal suckers (sprouts that grow out at the base of a tree).

\- Do not prune terminal leader or branch tips.

\- Prune any co-dominant leaders or narrow crotch angles.

\- Prune rubbing or crossed branches.

\- Prune any broken branches.

References

Arbor Day Foundation http://www.arborday.org/trees/NineNum8.cfm

American Forests http://www.americanforests.org/planttrees/howto.php

Virginia Department of Forestry http://www.dof.virginia.gov/mgt/how-to-plant.shtml

Watering Trees

Wayne K. Clatterbuck Associate Professor Forestry, and Larry Tankersley Extension Forester Forestry, Wildlife & Fisheries University of Tennessee

Water is the most limiting factor for tree survival and growth. Trees use water during photosynthesis and lose water during transpiration. Drought conditions can lead to tree decline, making the tree more susceptible to pest problems. Supplemental watering should be part of the tree-maintenance plans, especially during periods of water deficits and in areas where surface temperatures are escalating.

How to Water?

Ideally, watering should begin when soil moisture reaches some critical level. However, most homeowners do not have the instrumentation to measure soil moisture. Thus, precipitation events should be monitored and the soil observed to evaluate when watering is needed. Trees should be watered before they show symptoms of leaf curling or leaf detachment due to a lack of moisture.

The best way to water trees is gradually with a soaker hose or by trickle or drip irrigation. Sprinklers are less efficient, but they are easy to use. Use an organic mulch to conserve moisture and apply water over the top of the mulch. Do not concentrate the water at the base of the tree. Most of the fine feeder roots of trees are located several feet from the trunk. Excessive watering at the base of the tree can lead to pest problems and root diseases.

Where to Water?

Watering should take place beneath the crown of the tree and extending a few feet beyond the drip line of the crown. Trees need not be watered closer than 3 feet to the base of the trunk and not much beyond the drip line. These are the areas generally beneath the foliage and shaded by the tree. Be sure that the water slowly soaks into the soil and does not run off. Use mulch and slow application rates and growth. Grass and other landscape plants adjacent to trees will also benefit from deep-soaking water. Young, recently planted, ball-and-burlap trees also require frequent watering. Since water moves downward more than sideways, application of water should be directly over the planting area or the root ball.

When to Water?

The best time to water is during the evening hours and at night. Trees have a chance to replenish their moisture during these hours when they are not as stressed by hot temperatures. Watering at night allows effective use of water and less evaporative loss.

How Much Water and How Often?

The amount of water used in irrigation will depend on soil texture and structure, temperatures and the amount and timing of previous precipitation. Trees in limited rooting areas (thin soils), in containers or pots, on slopes, adjacent to warmer surfaces and in sandy soils will probably need more water. Trees in heavier soils with greater water-holding capacity will require less water. Over watering these sites often leads to anaerobic soil conditions, leading to root diseases or death.

Example of mulched areas free of vegetation under the drip line of trees. Watering should be concentrated in these areas.

Water use by trees increases with increasing temperatures. Trees surrounded by pavement or adjacent to other energy-absorbing, increased-temperature surfaces can be 20 to 30 degrees warmer than normal soil surfaces. For every 18- to 20-degree increase in temperature, the amount of water lost by a tree nearly doubles.

Trees should be watered once or twice a week in the growing season if there is limited rainfall. A few, high-volume waterings are more beneficial than many light and shallow waterings. Light waterings encourage shallow rooting, which can lead to more damage during lengthy drought. Once watering begins, it should be continued throughout the drought period when precipitation is limited.

Other Items

Other plants near the tree(s) compete for available water. The competition for water can be severe. Removing some of this competing vegetation from around the tree will reduce moisture stress. Use mulch to conserve soil moisture and prevent weed competition.

Late in the growing season (September) as the days get shorter and the temperatures get cooler, trees are preparing for the winter. Many of the leaves look unhealthy as they curl, become spotty in appearance and begin to change color or discolor. This is a normal part of the aging process as leaves begin to senesce. Watering during this time may be necessary when soils are excessively dry. However, the amount of water and the frequency of watering should be curtailed as the tree does not require as much water for transpiration and photosynthesis.

Summary

More long-term planning and research is needed to develop moisture-efficient landscapes to conserve water. Even so, supplemental watering will assist trees during periods of drought, high temperatures, and other water-loss events.

References

K.D. Coder. 1999. Watering Trees. University of Georgia, Warnell School of Forest Resources, Athens, GA

Mulching Your Trees

Wayne K. Clatterbuck Associate Professor Forestry, Wildlife & Fisheries University of Tennessee

What Is Mulch?

A protective covering of various materials, either organic or inorganic, spread over the soil surface to reduce evaporation of moisture, improve plant growth, discourage weedy species and enhance the appearance of the landscape is known as mulch. Inorganic mulching materials include landscape fabric and plastic film that are primarily used for weed control and retention of soil moisture, while rocks, gravel, brick chips and shredded rubber are used more for decorative purposes. Most inorganic mulches do not decay and thus do not improve soil properties. Grass clippings, straw, pine needles, leaves, peat moss, compost, wood fiber and bark are organic mulches composed of decaying plant materials. Over time, organic mulches will decompose and become part of the soil, adding to the soil's organic matter, improving soil structure and nutrient availability and helping the soil retain moisture. However, as the organic mulches decompose, they must be replenished.

Benefits of Mulch

Mulch has many benefits:

\- Moderates the temperature of the root zone.

\- Encourages the conservation of moisture in the soil by reducing surface evaporation.

\- Helps control weeds.

\- Prevents the soil from crusting over, allowing water to penetrate and percolate.

\- Improves soil aeration, soil structure (less soil compaction) and drainage.

\- Adds organic matter to the soil, improving fertility.

\- Restrains soil erosion, especially raindrop erosion.

\- Reduces the chance of mechanical injury to trees and shrubs from lawn mowers and weed trimmers.

\- Gives the landscape a more pleasing, manicured appearance.

Proper Use of Mulch

Mulch should be applied in a ring at least 4 to 6 feet in diameter around the base of the tree. The depth of mulch should be no more than 2 to 4 inches, tapering out to the ground level at the edge of the ring. The farther out from the tree you can make the mulch ring, the greater benefit to the tree. The larger the area that is mulched, the less tree roots must compete with the lawn for water and nutrients. Roots usually extend well beyond the drip line of the tree crown. Do not pile mulch against tree trunks. Pull mulch several inches away from the trunk so that the base of the trunk is exposed and air moves freely.

Improper Use of Mulch

Even with the many benefits of mulch, improper application can have a detrimental effect on trees. Most plants are sensitive to the depth of mulch. More than 4 inches of mulch restricts soil oxygen exchange with the roots.

A common practice in many landscapes is "volcano" mulching – the placing of mulch in a cone around and next to the trunk 8 to 12 inches high and extending horizontally about 2 feet in diameter. This depth of mulch restricts oxygen exchange with the roots, but also creates a moist environment at an elevated position near the base of the stem. This moist environment promotes cracking of the bark, creating an entry point for insects and fungal growth as well as conditions favorable for rodents to chew the bark and damage or girdle the tree.

Use of mulch that has not been properly composted or aged can create problems for many plants. Fresh grass clippings produce heat as they decay that may injure young plants. Other mulches, particularly fresh sawdust or wood wastes, do not contain adequate nitrogen for microorganisms to decompose them. Mulch can also change the pH of the soil, influencing nutrient availability. Some materials, such as pine needles and oak leaves, are more acid, while grass clippings and hardwood bark are more alkaline. Anaerobic or "sour" mulch in materials that have not been properly composted have pungent odors that build from the production of alcohols and organic acids. These compounds can be harmful to young plants and should be avoided by using composted materials rather than fresh mulch.

Summary

Deciding which mulch is best for you will depend on your purpose, preferences and associated costs. Before choosing mulch, consider how you will use it. Organic mulches are more natural and enhance many soil properties, while inorganic mulches are used more for decorative purposes. Both kinds of mulch conserve soil moisture to some extent and provide some weed control. All mulches have different properties that may be advantageous in some situations and detrimental in others. Make sure that mulch is applied correctly to enhance tree growth and that cured or aged materials are used.

References

Crater, D. 1999. Landscape mulching materials. The University of Tennessee Agricultural Extension Service Publication PB 713. Knoxville. 11 p.

International Society of Arboriculture (ISA). 2002. Proper mulching techniques. Champaign, IL. 3 p.

Relf, D. 2001. Mulching for a healthy landscape. Virginia Cooperative Extension Publication 426-724, Virginia Tech University, Blacksburg. 4 p

Samples, T and M.A. Nash. 2001. Composting yard, garden and food wastes at home. The University of Tennessee Agricultural Extension Service Publication PB 1479. Knoxville. 8 p.

Sams, D.W. 1998. Mulching vegetable gardens. The University of Tennessee Agricultural Extension Service Publication SP 291-H. Knoxville. 2 p.

Starbuck, C.J. 1998. Mulches. University of Missouri-Columbia Agricultural Publication G06960. 10 p.

How To Prune A Tree

Peter J. Bedker, Joseph G. O'Brien, and Manfred M. Mielke – USDA Forest Service

All landscape and shade trees require pruning at some time during their life. Trees may be pruned to:

\- Promote plant health by removing dead or dying branches injured by disease, severe insect infestation, animals, storms, or other adverse mechanical damage such as crossing and rubbing branches;

\- Maintain the intended purposes in a landscape, by encouraging flower and fruit development, maintaining a dense hedge, or maintaining a desired tree form or special garden forms;

\- Improve aesthetics by controlling plant size or removing unwanted branches, waterspouts, suckers, and undesirable fruiting structures;

\- Protect people and property by removing dead or hazardous branches such as weak or narrow-angled tree branches that overhang homes, parking areas, and sidewalks;

\- Increase visibility by eliminating branches that interfere with street lights, traffic signals, overhead wires, or obscure vision at intersections; and

- Improve security around the home by removing branches that obscure the entry to your home.

Pruning can best be used to encourage trees to develop a strong structure and reduce the likelihood of damage during severe weather. Pruning for form can be especially important on open-grown trees that do very little self-pruning. All woody plants shed branches in response to shading and competition. Branches that are poorly attached may be broken off by wind and accumulation of snow and ice. Branches removed by such natural forces often result in large, ragged wounds that rarely seal. Pruning as a cultural practice can be used to supplement or replace these natural processes and increase the strength and longevity of plants.

Pruning Approaches

Proper pruning cuts are made at a node, the point at which one branch or twig attaches to another. In the spring of the year growth begins at buds, and twigs grow until a new node is formed. The length of a branch between nodes is called an internode. The most common types of pruning are:

\- Crown thinning primarily for hardwoods, is the selective removal of branches to increase light penetration and air movement throughout the crown of a tree.

\- Crown raising is the practice of removing branches from the bottom of the crown of a tree to provide clearance for pedestrians, vehicles, buildings, lines of site, or to develop a clear stem for timber production.

\- Crown reduction pruning is most often used when a tree has grown too large for its permitted space. This method, sometimes called drop crotch pruning, is preferred to topping because it results in a more natural appearance, increases the time before pruning is needed again, and minimizes stress.

Figure 1. Common types of pruning. Branches to be removed are in blue. Cuts should be made where indicated with red lines.

Pruning Cuts

Pruning cuts should be made so that only branch tissue is removed and stem tissue is not damaged. At the point where the branch attaches to the stem, branch and stem tissues remain separate, but are contiguous. If only branch tissues are cut when pruning, the stem tissues of the tree will probably not become decayed, and the wound will seal more effectively.

Pruning Live Branches

To find the proper place to cut a branch, look for the branch collar that grows from the stem tissue at the underside of the base of the branch. On the upper surface, there is usually a branch bark ridge that runs (more or less) parallel to the branch angle, along the stem of the tree. A proper pruning cut does not damage either the branch bark ridge or the branch collar.

Figure 2. Pruning cuts.

A proper cut begins just outside the branch bark ridge and angles down away from the stem of the tree, avoiding injury to the branch collar. Make the cut as close as possible to the stem in the branch axil, but outside the branch bark ridge, so that stem tissue is not injured and the wound can seal in the shortest time possible. The second cut should be outside the first cut, all the way through the branch, leaving a short stub. The stub is then cut just outside the branch bark ridge/branch collar, completing the operation.

Pruning Dead Branches

Prune dead branches in much the same way as live branches. Making the correct cut is usually easy because the branch collar and the branch bark ridge can be distinguished from the dead branch, because they continue to grow. Make the pruning cut just outside of the ring of woundwood tissue that has formed, being careful not to cause unnecessary injury.

Drop Crotch Cuts

A proper cut begins just above the branch bark ridge and extends through the stem parallel to the branch bark ridge. Usually, the stem being removed is too large to be supported with one hand, so the three cut method should be used.

\- With the first cut, make a notch on the side of the stem away from the branch to be retained, well above the branch crotch.

\- Begin the second cut inside the branch crotch, staying well above the branch bark ridge, and cut through the stem above the notch.

\- Cut the remaining stub just inside the branch bark ridge through the stem parallel to the branch bark ridge.

Figure 3. Pruning cuts.

To prevent the abundant growth of sprouts on the stem below the cut, or dieback of the stem to a lower lateral branch, make the cut at a lateral branch that is at least one-third of the diameter of the stem at their union.

References

ANSI Z133.1. 1994. Safety standards. American national standard for tree care operators. Washington, DC: American National Standards Institute.

ANSI A300. 1995. Standard practices for tree, shrub, and other woody plant maintenance. Washington, DC: American National Standards Institute.

Fazio, J. R. ed. 1992. Don't top trees. Tree City USA Bulletin No. 8. Nebraska City, NE: The National Arbor Day Foundation.

Harris, R.W. 1994. Clarifying certain pruning terminology: thinning, heading, pollarding. Journal of Arboriculture 20:50-54.

ISA Performance Guidelines Committee. 1994. Tree-pruning guidelines. Savoy, IL: International Society of Arboriculture.

Ryan, H.D.P. III. 1994. Arboricultural pruning methodologies. Arborist News Volume 3(4):33-38.

Shigo, A. 1991. Modern arboriculture. Durham, NH: Shigo & Trees, Associates.

Shigo, A. 1989. Tree pruning: a worldwide photo guide. Durham, NH: Shigo & Trees, Associates

Pruning Trees and Shrubs

Mike Zins and Deborah Brown, Extension Horticulturists http://www.extension.umn.edu/distribution/horticulture/DG0628.html

Pruning Young Trees

International Society of Arboriculture (ISA)

Proper pruning is essential in developing a tree with a strong structure and desirable form. Trees that receive the appropriate pruning measures while they are young will require little corrective pruning when they mature. Keep these few simple principles in mind before pruning a tree:

\- Each cut has the potential to change the growth of the tree. Always have a purpose in mind before making a cut.

\- Proper technique is essential. Poor pruning can cause damage that lasts for the life of the tree. Learn where and how to make the cuts before picking up the pruning shears.

\- Trees do not heal the way people do. When a tree is wounded, it must grow over and compartmentalize the wound. As a result, the wound is contained within the tree forever.

\- Small cuts do less damage to the tree than large cuts. For that reason, proper pruning (training) of young trees is critical. Waiting to prune a tree until it is mature can create the need for large cuts that the tree cannot easily close.

Making The Cut

Where you make a pruning cut is critical to a tree's response in growth and wound closure. Make pruning cuts just outside the branch collar. Because the branch collar contains trunk or parent branch tissues, the tree will be damaged unnecessarily if you remove or damage it. In fact, if the cut is large, the tree may suffer permanent internal decay from an improper pruning cut.

If a permanent branch is to be shortened, cut it back to a lateral branch or bud. Internodal cuts, or cuts made between buds or branches, may lead to stem decay, sprout production, and misdirected growth.

Pruning Tools

When pruning trees, it is important to have the right tool for the job. For small trees, most of the cuts can be made with hand pruning shears (secateurs). The scissor-type, or bypass blade hand pruners, are preferred over the anvil type. They make cleaner, more accurate cuts. Cuts larger than one-half inch in diameter should be made with lopping shears or a pruning saw.

Never use hedge shears to prune a tree. Whatever tool you use, make sure it is kept clean and sharp.

Establishing a Strong Scaffold Structure. A good structure of primary scaffold branches should be established while the tree is young. The scaffold branches provide the framework of the mature tree. Properly trained young trees will develop a strong structure that requires less corrective pruning as they mature.

The goal in training young trees is to establish a strong trunk with sturdy, well-spaced branches. The strength of the branch structure depends on the relative sizes of the branches, the branch angles, and the spacing of the limbs. Naturally, those factors vary with the growth habit of the tree. Pin oaks and sweetgums, for example, have a conical shape with a central leader. Elms and live oaks are often wide spreading without a central leader. Other trees, such as lindens and Bradford pears, are densely branched. Good pruning techniques remove structurally weak branches while maintaining the natural form of the tree.

Trunk Development

For most young trees, maintain a single dominant leader growing upward. Do not prune back the tip of this leader. Do not allow secondary branches to outgrow the leader. Sometimes a tree will develop double leaders known as co-dominant stems. Co-dominant stems can lead to structural weaknesses, so it is best to remove one of the stems while the tree is young.

The lateral branches growing on the sides contribute to the development of a sturdy well-tapered trunk. It is important to leave some of these lateral branches in place, even though they may be pruned out later. These branches, known as temporary branches, also help protect the trunk from sun and mechanical injury. Temporary branches should be kept short enough not to be an obstruction or compete with selected permanent branches.

Permanent Branch Selection

Nursery trees often have low branches that may make the tree appear well-proportioned when young, but low branches are seldom appropriate for large-growing trees in an urban environment. How a young tree is trained depends on its primary function in the landscape. For example, street trees must be pruned so that they allow at least 16 feet of clearance for traffic. Most landscape trees require only about 8 feet of clearance.

The height of the lowest permanent branch is determined by the tree's intended function and location in the landscape. Trees that are used to screen an unsightly view or provide a wind break may be allowed to branch low to the ground. Most large-growing trees in the landscape must eventually be pruned to allow head clearance.

The spacing of branches, both vertically and radically, in the tree is very important. Branches selected as permanent scaffold branches must be well spaced along the trunk. Maintain radial balance with branches growing outward in each direction.

A good rule of thumb for the vertical spacing of permanent branches is to maintain a distance equal to 3 percent of the tree's eventual height. Thus, a tree that will be 50 feet tall should have permanent scaffold branches spaced about 18 inches apart along the trunk. Avoid allowing two scaffold branches to arise one above the other on the same side of the tree.

Some trees have a tendency to develop branches with narrow angles of attachment and tight crotches. As the tree grows, bark can become enclosed deep within the crotch between the branch and the trunk. Such growth is called included bark. Included bark weakens the attachment of the branch to the trunk and can lead to branch failure when the tree matures. You should prune branches with weak attachments while they are young.

Avoid over thinning the interior of the tree. The leaves of each branch must manufacture enough food to keep that branch alive and growing. In addition, each branch must contribute food to grow and feed the trunk and roots. Removal of too many leaves can "starve" the tree, reduce growth, and make the tree unhealthy. A good rule of thumb is to maintain at least half the foliage on branches arising in the lower two-thirds of the tree.

Harmful Pruning Practices

Peter J. Bedker, Joseph G. O'Brien, and Manfred M. Mielke – USDA Forest Service

The pruning of large trees is best left to qualified tree care professionals who have the proper equipment. However some common pruning practices exist that may cause excessive harm to trees. If these poor pruning practices are being applied to your trees, halt the job and seek help from a qualified individual or firm.

Timing

Trees should be pruned at the appropriate time of year. Although conifers may be pruned any time of year, pruning during the dormant season may minimize sap and resin flow from cut branches.

Hardwood trees and shrubs without showy flowers, however, should be pruned in the dormant season to easily visualize the structure of the tree, to maximize wound closure in the growing season after pruning, to reduce the chance of transmitting disease, and to discourage excessive sap flow from wounds. Dead branches can be removed any time of the year.

Topping and Tipping

Topping and tipping are pruning practices that harm trees and should not be used. Crown reduction pruning is the preferred method to reduce the size or height of the crown of a tree, but is rarely needed and should be used infrequently. Topping, the pruning of large upright branches between nodes, is sometimes done to reduce the height of a tree. Tipping is a practice of cutting lateral branches between nodes to reduce crown width. These practices invariably result in the development of epicormic sprouts, or in the death of the cut branch back to the next lateral branch below. These epicormic sprouts are weakly attached to the stem and eventually will be supported by a decaying branch.

Improper pruning cuts cause unnecessary injury and bark ripping. Flush cuts injure stem tissues and can result in decay. Stub cuts delay wound closure and can provide entry to canker fungi that kill the cambium, delaying or preventing wound-wood formation.

Pruning Tools

Proper tools are essential for satisfactory pruning. The choice of which tool to use depends largely on the size of branches to be pruned and the amount of pruning to be done. Tools should be clean and sanitized as well as sharp. Although sanitizing tools may be inconvenient and seldom practiced, doing so may prevent the spread of disease from infected to healthy trees on contaminated tools. Tools become contaminated when they come into contact with fungi, bacteria, viruses and other microorganisms that cause disease in trees. Most pathogens need some way of entering the tree to cause disease, and fresh wounds are perfect places for infections to begin. Microorganisms on tool surfaces are easily introduced into susceptible trees when subsequent cuts are made. The need for sanitizing tools can be greatly reduced by pruning during the dormant season.

If sanitizing is necessary it should be practiced as follows: Before each branch is cut, sanitize pruning tools with either 70% denatured alcohol, or with liquid household bleach diluted 1 to 9 with water (1 part bleach, 9 parts water). Tools should be immersed in the solution, preferably for 1-2 minutes, and wood particles should be wiped from all cutting surfaces. Bleach is corrosive to metal surfaces, so tools should be thoroughly cleaned with soap and water after each use.

Treating wounds

Tree sap, gums, and resins are the natural means by which trees combat invasion by pathogens. Although unsightly, sap flow from pruning wounds is not generally harmful; however, excessive "bleeding" can weaken trees.

When oaks or elms are wounded during a critical time of year (usually spring for oaks, or throughout the growing season for elms) — either from storms, other unforeseen mechanical wounds, or from necessary branch removals — some type of wound dressing should be applied to the wound. Do this immediately after the wound is created. In most other instances, wound dressings are unnecessary, and may even be detrimental. Wound dressings will not stop decay or cure infectious diseases. They may actually interfere with the protective benefits of tree gums and resins, and prevent wound surfaces from closing as quickly as they might under natural conditions. The only benefit of wound dressings is to prevent introduction of pathogens in the specific cases of Dutch elm disease and oak wilt.

References

ANSI Z133.1. 1994. Safety standards. American national standard for tree care operators. Washington, DC: American National Standards Institute.

ANSI A300. 1995. Standard practices for tree, shrub, and other woody plant maintenance. Washington, DC: American National Standards Institute.

Fazio, J. R. ed. 1992. Don't top trees. Tree City USA Bulletin No. 8. Nebraska City, NE: The National Arbor Day Foundation.

Harris, R.W. 1994. Clarifying certain pruning terminology: thinning, heading, pollarding. Journal of Arboriculture 20:50-54.

ISA Performance Guidelines Committee. 1994. Tree-pruning guidelines. Savoy, IL: International Society of Arboriculture.

Ryan, H.D.P. III. 1994. Arboricultural pruning methodologies. Arborist News Volume 3(4):33-38.

Shigo, A. 1991. Modern arboriculture. Durham, NH: Shigo & Trees, Associates.

Shigo, A. 1989. Tree pruning: a worldwide photo guide. Durham, NH: Shigo & Trees, Associates

Pruning Trees and Shrubs Mike Zins and Deborah Brown, Extension Horticulturists http://www.extension.umn.edu/distribution/horticulture/DG0628.html

Tree Support Systems

Wayne K. Clatterbuck Associate Professor Forestry, Wildlife & Fisheries University of Tennessee  
David S. Vandergriff, UT Extension Urban Horticulture & Forestry

Urban trees often need some degree of supplemental, physical support to reduce the risk of structural failure of the crown or root system. Cabling, bracing, guying and staking can provide a solution for these tree failures. Tree support systems help support the tree by limiting the movement of branches, leaders or the entire tree. This reduces the risk of injury to humans and damage to property by providing supplemental support for structurally weak areas of the tree.

Common Structural Deficiencies in Trees

The most common risk of tree breakage is the presence of one or more codominant stems. Codominant stems, or "v-crotches," are structurally weak compared to a single stem. This is due to the lack of connective tissue anchoring a stem to the tree trunk and the presence of included bark between the stems. The greater the angle of the "v-crotch," the greater the risk of structural failure. The best solution for problems associated with codominant stems is to buy and plant trees with a single leader. An alternative is to remove one of the codominant stems as early as possible in a tree's life, allowing for the development of a single leader. Otherwise, bracing or cabling is required to strengthen the weak area of the tree.

Another condition that often results in structural problems is the presence of long, heavy or "overextended" limbs. These are limbs that are unusually long for the tree species or grow horizontally or downward, with most of the foliage concentrated toward the end of the branch. Breakage resulting from these conditions often occurs at the junction of the branch and stem. Alternately, the branch may crack due to the forces of tension and compression. These failures usually occur when the branch is under heavy loading such as wind, snow or ice. Installation of cables may be used to avoid making large pruning cuts. Early corrective pruning is the best course of action to prevent this condition.

A third structural problem is a weakly anchored tree. Poorly anchored trees are the result of transplanting a tree with a substandard root ball, a compromised root system with root damage or decay, or planting in shallow or compacted soils. Pruning, tree removal, installation of support devices such as cables, brace bolts and guys, or a combination of these techniques may be recommended.

Tree Support Devices

Brace rods are used when multiple leaders exist in the tree. These rods reduce the risk of the leaders spreading apart or moving sideways in relation to each other. Brace rods are also used to repair a crotch or branch that has split.

Brace rods are typically accompanied by at least one cable for additional support. Brace rods are installed as either a through rod (rod is bolted with a nut on other side of tree or branch) or dead-end (rod is threaded into the tree) configuration.

Cabling restricts the distance that a branch can move in relation to the rest of the tree. Cables are installed across a weak crotch to reduce the risk of a branch breaking. Cables are also installed on overextended branches to support the branch. More than one cable is often necessary in the installation and may be used in combination with brace rods.

Guying is where a cable is installed between the tree and an external anchor to provide supplemental support and to reduce tree movement. Trees with root problems may be guyed to keep them upright and protect potential targets if they fail. Established trees are guyed if they have had some degree of tipping from wind throw and require some support.

Tree staking is used to hold the tree upright and the root ball in place until the roots become established in the surrounding soil. Staking can also be used to straighten the trunk of a young tree or protect the lower trunk from injury. Generally, staking is discouraged because most trees with adequate root systems do not need to be staked at planting. Trees that are staked require constant monitoring and maintenance.

Trees can be staked aboveground or belowground. Aboveground staking should be installed as low in the tree as possible. The root ball can also be anchored belowground by driving metal or wooden stakes along the sides of the root ball about a foot deeper than the root ball. This eliminates the need for aboveground staking and maintenance.

References

Harris, R.W., J.R. Clark and N.P. Matheny. 2004. Arboriculture: Integrated Management of Landscape Trees, Shrubs, and Vines. Prentice Hall, Upper Saddle River, NJ. 578 p.

National Arborist Association, Inc. 2000. Support Systems (Cabling, Bracing and Guying Established Trees), ANSI

A300, Part 3. American National Standard for Tree Care Operations – Tree, Shrub, and other Woody Plant Maintenance – Standard Practices. Manchester, NH. 11 p.

Smiley, E.T. and S. Lilly. 2001. Tree Support Systems: Cabling, Bracing and Guying. Best Management Practices Series. International Society of Arboriculture, Champaign, IL. 30 p.

Watson, G.W. and E.B. Himelick. 1997. Principles and Practice of Planting Trees and Shrubs. International Society of Arboriculture, Savoy, IL. 199 p.

Post-Planting Tree Care

Wayne K. Clatterbuck Assistant Professor Forestry, Wildlife & Fisheries University of Tennessee

Most trees experience shock after transplanting because of the disturbance to the root system. In balled and burlapped transplants, it is estimated that 4 to 9 percent of the original root system and about 2 percent of the soil volume occupied by the root system in the nursery is contained in the root ball. Trees try to keep a balance between the above-ground portion of the tree and the root system (Perry 1982). When the amount of the root system is reduced during transplanting, the above-ground portion of the tree is also affected. The tree either is stimulated to regenerate more roots to balance the top, or the top partially dies back, or both so that the shoots and the roots establish equilibrium.

Thus, transplanting success depends primarily on the care of the root system before and after transplanting. For this reason, post-planting tree care as discussed in this fact sheet is extremely important.

Recommendations

Watering

Water is the most critical factor in transplanting success! Keeping the soil moist, but not wet, through watering is the best avenue to ensure survival and growth of your transplanted tree. Different species of trees and different soils make a general, overall watering recommendation unrealistic. When watering a tree, apply enough to thoroughly soak the soil in the root zone. Transplanted trees require more water than they did in the nursery. Frequent watering of transplants provides more benefit than applying large volumes of water infrequently because of the smaller root system. Drip irrigation systems and water reservoir devices can facilitate watering. Proper water management is the key for establishing transplants quickly.

Mulch

Apply mulch 2 to 3 inches deep on the surface of the planting hole and extending perhaps 2 or more feet beyond the perimeter of the hole. Organic mulch will conserve water in the soil; allow better infiltration of water into the soil during rainfall events or watering and helps to prevent weeds. Do not place mulch against the tree trunk or apply mulch too thickly. Excessive use of mulch can induce fermentation, immobilize nutrients, cut off the oxygen supply and kill trees (Perry 1982).

Size of Planting Hole

The planting hole should be at least 2 or 3 times as wide, and in some cases, where soils are compacted, up to 5 times as wide as the root ball. Wide, shallow holes encourage horizontal root growth by decreasing the resistance for root penetration into the native soil. The larger planting hole and loosened backfill expedites root growth. The sooner the roots are able to penetrate and grow into the native soil, the sooner the tree will become fully established after transplanting.

Score Root Balls

If roots are circling around the root ball exterior, cut through the roots in a few places. Circling roots are usually found in container stock. Cutting helps prevent circling roots from eventually girdling the trunk and also initiates root regeneration and growth that increases the probability that roots will grow from the container medium into the native soil.

Fallacies

Addition of Soil Amendments

Backfill planting holes with existing unamended soil. Do not incorporate organic matter such as peat moss into the backfill. Differences in soil pore sizes will be created, causing problems with water movement, water retention and root growth between the root ball, planting hole and surrounding soil. Backfill half of the planting hole and water thoroughly to settle out air pockets. Water again once back-filling is completed.

Addition of Fertilizer

Research on trees transplanted from field nurseries indicates that there is little benefit to fertilizing at planting (Van de Werken 1981). Since most tree roots are in the upper 12 inches of the soil, trees will receive some benefit when fertilizing turfgrass (Tankersley and Samples 1999). Fertilizer should not be incorporated in the backfill during planting, where it could easily damage exposed tree roots.

Use of Tree Wraps, Shelters and Staking

Tree wraps, tree shelters and tree staking are used frequently to protect trees from external influences. If cared for and maintained properly and regularly, these materials are worthwhile. Experience indicates that treated trees are not usually well maintained at regular intervals and these treatments ultimately are detrimental to the health of trees. In the majority of situations, use of these materials is not recommended unless absolutely necessary. The potential injuries incurred by using these protective measures outweigh their benefits.

Summary

Providing advantageous conditions for tree root growth increases the probabilities of successfully transplanting trees. Proper water management in the first several months after transplanting reduces the stressful establishment period by promoting rapid root growth. Trees that regenerate roots rapidly and establish more quickly will provide many benefits to your landscape.

References

Appleton, Bonnie L. and Susan French. 1996. Tree and shrub planting guidelines. Virginia Cooperative Extension Publication 430-295. Virginia Tech University, Blacksburg, VA. 3 p.

Clatterbuck, Wayne K. 1999. Effect of tree shelters on growth of hardwood seedlings after seven growing seasons. In Proc. 10th Biennial Southern Silvicultural Research Conf.(J. Haywood, ed.). p. 43-46. USDA Forest Service General Technical Report SRS-30, Asheville, NC.

Conlon, Hubert P. and Wayne K. Clatterbuck. 1999. Fertilizing landscape trees. The University of Tennessee, Agricultural Extension Service SP 548. Knoxville, TN. 4 p. Gilman, Edward F. 1994. Establishing trees in the landscape. In The Landscape Below Ground: Proc. of an International Workshop on Tree Root Development in Urban Soils (Gary W. Watson and Dan Neely, eds). p. 69-77. International Society of Arboriculture, Savoy, IL.

Perry, Thomas O. 1982. The ecology of tree roots and the practical significance thereof. Journal of Arboriculture 8(8): 197-211.

Tankersley, Larry and Tom Samples. 1999. Managing trees and turfgrasses. The University of Tennessee, Agricultural Extension Service SP 535. Knoxville, TN. 4 p.

Van de Werken, H. 1981. Fertilization and other factors enhancing growth rate of young shade trees. Journal of Arboriculture 7:33-37.

Watson, Gary W. 1994. Root development after transplanting. In The Landscape Below Ground: Proc. of an International Workshop on Tree Root Development in Urban Soils (Gary W. Watson and Dan Neely, eds). p. 54-68. International Society of Arboriculture, Savoy, IL.

Williams, Don. 1988. Basic care of trees, shrubs and lawns around public buildings in Tennessee. The University of Tennessee, Agricultural Extension Service EC 965. Knoxville, TN. 14 p.

Replanting After A Storm

Mary L. Duryea Resource Extension Specialist University of Florida

After all the structural damage has been repaired and the debris from downed trees removed, homeowners may ask how to regenerate the beauty of their ornamental landscape. Since trees are at the core of any well-landscaped property, it is important to do some planning before visiting the local nursery. Selecting the RIGHT place, planting it the RIGHT way and at the RIGHT time, will not only assure a lifetime of satisfaction, but also will keep maintenance costs low and maximize your investment.

Selecting the right tree

In selecting the RIGHT tree, it is important to know the purpose you have for that tree in the landscape. Whether you are planting for shade, aesthetics, windbreaks, delineating properties, or for wildlife, you need to remember that trees have many different characteristics that will affect their function. A tree's growth habit and shape need to be considered:

\- Mature size is very important. The tree should not outgrow its allotted space.

\- Tree forms vary among species as much as leaf shapes and bark patterns.

\- Fast growing trees are usually tolerant of difficult sites, but are also usually weak-wooded.

\- Wood strength and branching structure are closely allied in determining its ability to withstand wind and ice storms. Trees with well-shaped branches are inherently stronger.

\- Some species are known for their invasive and surface roots (willows and cottonwoods).

After selecting the tree characteristics that best suit the functions you are looking for in your landscape, you must consider what environmental factors limit the ability of a particular species to thrive in your area. It is very important to match the planting site's characteristics with the tree's growth requirements. These environmental factors include:

\- Temperature – Can the tree handle the minimum average annual temperature for your area? Select a species suitable for your USDA plant hardiness zone.

\- Moisture – Each species can tolerate wet or dry growing conditions to a different degree

\- Light – Know your tree's shade tolerance (low, medium, or full sunlight).

\- Pests – Every area has its problems with a particular insect or disease. Try to avoid species that host these pests.

\- Soil – Soil depth, structure, pH (acidity or alkalinity), compaction and drainage can make a difference between success or failure after planting.

Selecting the right place

When selecting the RIGHT place for a tree, remember the tree's size (height AND crown spread) at maturity to avoid conflicts with both above- ground and belowground permanent structures (buildings, sidewalks, power and phone lines, gas and sewer lines, etc.).

Planting the right way. Planting your trees the RIGHT way will help them become established quicker. It is better to "plant a $10 tree in a $100 hole, then to plant $100 tree in a $10 hole." Before digging, make sure you have located all underground utilities: SAFETY FIRST!

\- Dig a hole 2-3 times the size of the root ball, and only as deep as the root ball. Place the root ball in the hole so that the top of the root ball is level with the existing soil line.

\- Add soil around the base of the root ball to stabilize it in the hole. Remove string, wire or burlap from the top 10" of the root ball. Make sure tree is standing straight in all directions.

\- Finish adding soil (backfill with original soil only), GENTLY pack it until soil is level with existing soil. Create a watering basin around the tree with existing soil, making it 4" high and wider than the planting hole (knock down after one year).

\- Use organic material to mulch the entire loosened area, 3-4" deep, but keep it 2-3" away from the trunk to avoid decomposing the bark. Stake only if necessary, making sure to protect the tree bark from rubbing damage by running the supporting wire or rope through a piece of old garden hose, where it is placed around the tree. Do not stake so tightly that tree is not allowed to sway in the wind, and remove stakes after one year.

Water after planting and when necessary. Slow, less frequent and deep watering will encourage roots to grow deeper and protect them from drought. Check moisture levels down to 4" from the existing soil line, and water if dry.

Planting at the right time

Fall is the RIGHT time for planting. Planting in late fall through early spring allows trees to establish new roots before spring rains and summer heat stimulate new growth. Trees need an established root system to keep up with higher water demand in the summer. During the winter dormant season the roots will continue to grow while the top remains inactive.

Conclusion

Buying the RIGHT tree and planting it the RIGHT way in the RIGHT place will reduce the future pruning requirements and ensure that trees are healthy. So, remember to buy quality nursery stock and provide proper care throughout the tree's life.

What to Look For:

\- Even form

\- Foliage: good color with no insect damage

\- Healthy new leaves

\- Strong branch crotches

\- Single trunk or leader

\- Pruning scars are well sealed

\- Healthy well attached bark

\- Adequate root space

What to avoid:

\- Multiple leaders indicate tree has been topped

\- Foliage has pale color and/or has insect damage

\- Crossing branches

\- Weak crotches (narrow angles)

References

This document is Circular 1183, one of a series of the School of Forest resources and Conservation, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: May, 1997. Reviewed September 2006. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.

Mary L. Duryea, Ph.D., forest resource extension specialist, School of Forest Resources and Conservation, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611

Tree Damage and Hazard Assessment

Predicting Tree Failure

Gary R. Johnson Associate Professor Urban and Community Forestry University of Minnesota

Ben Johnson Undergraduate Research Assistant Department of Forest Resources University of Minnesota

The key to preventing damage is to predict circumstances that could result in tree damage and take action to correct potential problems before storms strike. Look at the form of the tree, present decay and its extent, maintenance practices involving the tree, the presence of stem girdling roots, and existing site problems. There may be other predictable situations present, but these factors are the most common.

Tree Form

Trees may suffer from several natural form imperfections that lead to damage under storm conditions. Inclusion of bark at branch unions is a common weak point in trees. Branch unions should have a rough, protruding branch bark ridge where the branches meet. Without this proper union, branches or leaders have a tendency to separate during storm situations. Trees may also have codominant leaders. This occurs when a tree has two or more branches or stems that are trying to become the center point of the tree. Codominant leaders typically exhibit inclusion at their unions.

Image 1: Codominant leader with included bark = poor form and potential hazard. Photo by Gary R. Johnson

Decay

Decay is the natural degradation of tree stem, branch, and root tissue. Degraded tissue has very little strength and is the most common contributor to tree failure. Location of decay within a tree is critical in assessing the tree's potential for failure. Decay located within a single branch is not always a critical situation since weak branches can easily be removed. But decay located within the main part of the trunk can be dangerous. Determining the extent of decay within the tree determines the tree's decay and potential to fail. For every 3 inches of branch or stem diameter, solid wood should comprise at least 1 to 1.5 inches. Anything less than that often indicates a branch or stem that is more likely to fail during a storm.

Maintenance

Poor maintenance practices may encourage decay anywhere in the tree. Mechanical damage, including wounds from lawnmowers/grass trimmers, and poor pruning practices, often leads to decay. Piling mulch several inches against the stem may lead to stem girdling roots and other dysfunctional root systems. Incorrect irrigation can over saturate a soil and can encourage shallow root systems, stem girdling roots, and unstable trees. Improper use of staking equipment (wires around stems) often girdles and weakens stems.

Poor pruning practices that encourage decay or the formation of weak branches include: flush cutting (pruning too close to the lead branch or trunk), leaving long stubs, "topping trees," or stripping bark when pruning. Trees should have between 2"-4" of coarse mulch, none of which is resting against the trunk of the tree. Staking equipment that is not properly installed or is left attached to the tree too long will damage stem tissue and encourage decay. Never attach staking wires or ropes to tree stems. Use wide, padding materials around the tree stem and connect these materials to the tree wires or ropes. There are several types of padding available at many garden centers or hardware stores, but strips of carpeting, old belts, or inner tubes also work well. No staking or guying materials should be left on a tree for more than 1 year without inspection and adjustment for increased stem growth.

Stem Girdling Roots

Stem girdling roots are roots at or below the soil surface that partially or completely encircle the trunk of the tree. Over time, they begin to stress the health of the tree, including the root system. The girdling roots eventually cause compression of the lower trunk, creating a weak point that is often the point of failure in high windstorms. Many stem girdling root problems can be prevented by root pruning pot bound trees before planting and planting all trees at the correct depth—the first branch roots just below the soil surface.

Site Problems

Common site problems that may contribute to tree failure are: poor soils, confined rooting areas, and inappropriate species for the location (such as large trees in small boulevard strips). Most of the problems are directly or indirectly related to lack of oxygen reaching the roots of the trees. When oxygen is lacking, root systems decline and tree stability declines. It is important to know your site situation, including soil types and rooting volume, before trees are selected and planted.

Image 3: Blow over as a result of shallow root system. Photo by Gary R. Johnson

Summary

While tree failure cannot be 100% predicted, there are ways to determine if tree failure is possible. Decay, poor maintenance practices, stem girdling roots, and site problems can be indicators of possible future damage. Take care to analyze these conditions and take preventative action if possible.

Tree Wounds

Wayne K. Clatterbuck Associate Professor Forestry, Wildlife & Fisheries University of Tennessee

Tree wounds are common and the causes include: broken branches; impacts, abrasions and scrapes; animal damage; insect attack; fire; etc. Wounds usually break the bark and damage the food and water conducting tissues. Wounds also expose the inside of the tree to organisms, primarily bacteria and fungi that may infect and cause discoloration and decay of the wood. Decay can result in structurally weakened tree stems and can shorten the life of a tree. Decay cannot be cured. However, proper tree care can limit the progress of decay in an injured tree. This fact sheet discusses tree responses to wounding and what can be done after wounding to keep the tree healthy.

Tree Response to Wounding:

Trees respond to wounding or injury in two ways: compartmentalization and the development of barrier zones (Shigo 1986).

Compartmentalization

When a tree is wounded, the injured tissue is not repaired and does not heal. Trees do not heal; they seal. If you look at an old wound, you will notice that it does not "heal" from the inside out, but eventually the tree covers the opening by forming specialized "callus" tissue around the edges of the wound. After wounding, new wood growing around the wound forms a protective boundary preventing the infection or decay from spreading into the new tissue. Thus, the tree responds to the injury by "compartmentalizing" or isolating the older, injured tissue with the gradual growth of new, healthy tissue.

Barrier Zones

Not only do trees try to close the damaged tissue from the outside, they also make the existing wood surrounding the wound unsuitable for spread of decay organisms. Although these processes are not well understood, the tree tries to avoid further injury by setting chemical and physical boundaries around the infected cells, reacting to the pathogen and confining the damage.

If the tree is fast and effective with its boundary-setting mechanisms, the infection remains localized and does not spread. However, if the boundary-setting mechanisms are not effective, the infection will spread. Most vigorous or actively growing trees are fairly successful in coping with decay-spreading mechanisms.

Care for Tree Wounds:

Proper care of tree wounds encourages callus growth and wound closure.

Physical Repair

Tree wounds often appear ragged where the bark is torn during the injury. This is common during branch breakage and when the trunk of the tree has been scraped. To repair this type of damage, cut off any ragged bark edges with a sharp knife. Take care not to remove any healthy bark and expose more live tissue than necessary. If possible, the wound should be shaped like an elongated oval, with the long axis running vertically along the trunk or limb. All bark around the wound should be tight.

Wound Dressings

Research indicates that wound dressings (materials such as tar or paint) do not prevent decay and may even interfere with wound closure. Wound dressings can have the following detrimental effects:

\- Prevent drying and encourage fungal growth

\- Interfere with formation of wound wood or callus tissue

\- Inhibit compartmentalization

\- Possibly serve as a food source for pathogens

For these reasons, applying wound dressings is not recommended. Trees, like many organisms, have their own mechanisms to deter the spread of decay organisms, insects and disease.

Cavity Filling

Filling large holes or hollows in the tree is generally done for cosmetic reasons. There is little data to indicate that a filled tree has better mechanical stability. However, fillings may give the callus tissue a place to seat, thus stopping the in-roll (folding) of the callus (Shigo 1982). Almost any filling can be used as long as it does not abrade the inside of the tree.

Filling a tree cavity is generally expensive and not recommended. Filling does not stop decay and often during the cleaning of the cavity, the boundary that separates the sound wood or the callus growth from the decayed wood is ruptured. Thus, this cleaning for cavity filling can have more detrimental effects on the tree than if it were left alone. Care must be taken not to damage the new callus tissue that has formed in response to the tree damage and subsequent decay.

Pruning Wounds

Proper pruning should be used to remove dead, dying and broken branches; to remove low, crossing or hazardous branches; and to control the size of the tree. However, pruning of any kind places some stress on the tree by removing food-producing leaves (if the branch is alive), creating wounds that require energy to seal, and providing possible entry points for disease.

Pruning cuts should be made to maximize the tree's ability to close its wound and defend itself from infection. When pruning, make clean, smooth cuts. Do not leave branch stubs. Leave a small collar of wood at the base of the branch. The branch collar is a slightly swollen area where the branch attaches to the trunk. Cutting the limb flush with the trunk will leave a larger area to callus over and a greater chance of decay organisms entering the wound. The optimal pruning time is in the winter (dormant season) when temperatures and infection rates are lower and when trees are not actively growing.

Conclusion. Healthy trees usually recover from wounding quickly. Try to keep wounded trees growing vigorously by watering them during droughts and providing proper fertilization. This will increase the rate of wound closure, enhance callus growth and improve the resistance to decay mechanisms.

References

Shigo, A.L. 1982. Tree health. Journal of Arboriculture 8(12):311-316.

Shigo, A.L. 1986. A New Tree Biology. Shigo Trees & Associates, Durham, NH. 595 p.

Prevention Of Tree Failure

Gary R. Johnson Associate Professor Urban and Community Forestry University of Minnesota

Ben Johnson Undergraduate Research Assistant Department of Forest Resources University of Minnesota

Inventory

By keeping track of trees on your property and their condition, preventing storm failure is much easier. Create a list of "key trees and key problems." Key trees would be those that are most important to the property. Key problems would be those that are most likely to damage or weaken those key trees.

Monitor

Check key trees regularly. When minor damage occurs, correction (such as pruning or wound "painting" on oaks during oak wilt season) may prevent it from causing extensive damage throughout the tree. If extensive damage has occurred, immediate corrective action should be applied to prevent further damage.

Proper Pruning

Pruning either corrects problems or creates them. If pruning is done improperly, it can create places for decay to enter and the wound will only increase in extent. Done correctly, pruning wounds should close over naturally, keeping decay from starting and expanding in the wound area. A general rule for pruning wounds: the smaller, the better.

Image 1: Flush cutting, i.e., cutting too far into living tissue, can provide sites of decay. Photo by Gary R. Johnson

Image 2: Leaving long stubs may also provide entrance sites for decay. Photo by Gary R. Johnson

Protection From Mechanical Wounding

Mulching, planting trees in landscaped beds, and even staking can give trees the necessary protection from mechanical injury. Wounds caused from lawnmowers and grass trimmers can promote areas of decay in the tree. Cars, snowplows, staples, and any stacked materials that wound stems and branches can cause long-term damage in a short time.

Appropriate Species

Using appropriate species in each site is extremely important. Many of the problems that homeowners face could be diminished just by using species that are native to the area or accustomed to the site conditions. For more information on tree species selection check the Texas Forest Service Tree Planting Guide at http://texastreeplant.tamu.edu.

Best Planting Practices. Planting too deep may be the most common planting mistake that leads to tree failure. Literature is available on proper planting techniques (see Fact Sheet 1.5). Most importantly, do not plant the tree too deep. The first set of roots should be just below the soil surface.

Image 3: Planting too deep hid a girdling root that caused stem compression. The stem failed several inches below ground. Photo by Diana Bolander

Image 4: Proper way to plant a tree. Illustration provided by the National Arbor Day Foundation, Tree City USA Bulletin No. 19

Image 5: Tree failure can have severe consequences--many of which can be prevented. Photo by Gary R. Johnson

Maintain Health

By watering properly and frequently, and by fertilizing when nutrients are deficient, tree health can be maintained at a high level. When trees are stressed, they become more susceptible to problems ranging from aesthetic (leaf scorch), to decay, to severe, uncorrectable damage from diseases or insects.

Assistance

City foresters, county Agrilife Extension offices, and tree care professionals are available to answer questions about tree care problems.

Summary

Planting the right tree in the right place is the first step in preventing tree damage. Proper care and maintenance of trees will also help to prevent damage.

Understanding Lightning And Associated Tree Damage

Wayne K. Clatterbuck, Associate Professor Forestry, Wildlife & Fisheries University of Tennessee, David S. Vandergriff, UT Extension Urban Horticulture & Forestry, Kim D. Coder Professor, Silvics/Ecology Warnell School of Forest Resources The University of Georgia

Lightning is one of nature's most powerful forces. Lightning can have devastating effects on people, property and trees. Each strike of lightning can reach more than five miles in length, and produce temperatures greater than 50,000 degrees Fahrenheit and an electrical charge of 100 million volts. At any given moment, there are 1,800 thunderstorms in progress somewhere across the earth. Lightning detection systems in the United States sense an average of 25 million lightning strikes per year.

Trees occupy a particularly susceptible position in the landscape, since they are often the tallest objects. Tall trees are the most vulnerable, especially those growing alone in open areas such as on hills, in pastures or near water. Many of these trees line our community streets and surround our homes, schools and businesses.

Response of Trees to Lightning

A tree's biological functions and/or structural integrity are affected by lightning strikes. Along the path of the strike, sap boils, steam is generated and cells explode in the wood, leading to strips of wood and bark peeling or being blown off the tree. If only one side of the tree shows evidence of a lightning strike, the chances of the tree surviving and eventually closing the wound are good. However, when the strike completely passes through the tree trunk, with splintered bark and exploded wood on each side, trees are usually killed.

Many trees are severely injured internally or below- ground by lightning despite the absence of visible, external symptoms. Lightning or electrical current passes from the trunk of the tree through the roots and dissipates in the ground. Major root damage from electricity may cause the tree to decline and die without significant aboveground damage. If the tree is in leaf, the leaves wilt and the tree will probably die within a few days. If the tree survives long enough to leaf out the following spring, then the chances of recovery are much greater. Watering and fertilization are suggested to reduce tree stress.

Generally, when lightning damage has created hazardous broken branches, corrective pruning should be done. However, waiting two to six months is recommended before doing major and expensive corrective pruning to assess whether the tree will recover. If during this waiting period, the tree shows no obvious signs of decline, then the pruning is probably worth the expense. Consult with a certified arborist for recommendations concerning the health of your damaged tree. Commonly prescribed practices are water management, bark repair, pruning, fertilization, pest management and tree monitoring. Expensive treatments should not be taken until the tree appears to be making a recovery. Otherwise, when it becomes obvious that the tree will not recover from the lightning strike, the tree should be removed.

Lightning Protection Systems for Trees

Historic, rare, and specimen trees, especially when they are the center of landscapes or they shade or frame recreational areas, are valuable and can be protected by a properly installed lightning protection system. Trees with special significance, or that people or animals might move under in a storm, should be protected. Trees closer than 25 feet from a building or structure should also be protected to minimize "side-flash." Parks, golf courses, and public buildings should have large or important trees protected to minimize liability risks.

Tree lightning protection is expensive in labor and materials. Lightning protection systems must be installed properly with correct materials to insure long-term protection. For example, aluminum should not be used for any link in a system, nor should solid wire of any type be used. It is essential to consult with a trained arborist or urban forester, and a lightning protection system installer before designing a protection system for a tree.

Lightning protection systems in trees do not attract lightning. The purpose of a protection system is to dilute and slowly release electrical charge potential between the ground and cloud. Trees are not good conductors of electricity but can act as a better conduit than air. Protection systems dissipate the electrical charge before it can build to high levels.

Summary

Lightning damage in trees is much more effectively prevented than repaired and is often less costly. Qualified arborists can recommend the installation of lightning protection systems where appropriate or the proper course of action if a tree has been struck by lightning.

Sources

Coder, K.D. 2004. Lightning damage in trees: the spark of death. Arborist News 13(3):35–43.

Curran, E.B., R.L. Holle and R.E. Lopez. 1997. Lightning fatalities, injuries and damage reports in the United States from 1959-1994. National Oceanic & Atmospheric Administration (NOAA) Technical Memorandum NWS SR-193. U.S. Department of Commerce, National Weather Service, Scientific Services Division, Southern Region, Fort Worth, TX. (www.nssl.noaa.gov/papers/techmemos/NWS-SR-193/techmemosr193.html)

Howland, R. 2003. A striking danger in trees. Tree Care Indus- try 14(5):40–42. National Arborist Association, Inc. 2001. American National Standard for Tree Care Operations, ANSI Z133.1. Manchester, NH. 31 p. National Arborist Association, Inc. 2002.

Lightning Protection Systems, ANSI A300, Part 4. American National Standard for Tree Care Operations – Tree, Shrub, and other Woody Plant Maintenance – Standard Practices Manchester, NH. 9 p.

National Fire Protection Association. 2004. Installation of lightning protection systems. Publication NFPA 780. Quincy, MA. 50 p. (www.nfpa.org)

Smiley, E.T., A.W. Graham, Jr., and S. Cullen. 2002. Lightning Protection Systems. Best Management Practices Series. International Society of Arboriculture, Champaign, IL. 40 p.

U.S. Department of Commerce, National Oceanic & Atmospheric Administration, National Weather Service. 2005. Lightning Safety Outdoors. (www.lightningsafety.noaa.gov/outdoors.html) and (www.noaa.gov/lightning.html)

How To Recognize And Prevent Tree Hazards

Larry Tankersley Extension Associate Forestry, Wildlife & Fisheries University of Tennessee

Trees benefit us in many ways. They can also cause major damage when limbs or whole trees fall on power lines, cars, houses or people. Usually, weakened trees give some warning signs of danger. By learning to recognize the signs and to follow-up with prompt, proper action, you can often manage this risk, saving yourself grief as well as money.

What is a Hazard Tree?

A tree failure occurs when a tree or large part of a tree breaks and falls. Trees become a potential hazard when there is a target. A target is a structure, vehicle or a person that would be struck by a falling tree or its parts. The target directly influences the degree of hazard. Consider the differences among a tree falling on a fence, a house or a person. A tree leaning over the bedroom is most hazardous. Trees near high-use areas are more of a risk than those near infrequently visited areas, as the probability of a person being hit is greater. Priorities for removal or corrective treatments depend on the hazard rating of the tree.

Tree age is important in hazard tree management. Every tree species has an inherent life span. Risk of failure increases with age. Longevity should be considered when evaluating existing tree hazards or selecting species to plant. Generally, longer-lived species are preferred, unless plans are made to maintain or periodically replace less persistent species. The environment in which a tree lives will also determine its hazard potential.

Observe the Trunk

Decay, a major cause of tree failure, is caused by fungi that weaken wood as they grow and reproduce. As healthy trees bend and sway, wood fibers slide past each other. Decaying tissues, however, are not flexible and often break. The presence of many reproductive structures often indicates advanced stages of decay. Decay is often present without obvious signs. Cracks, seams, butt swell, dead branch stubs and large, older wounds suggest internal decay.

Wounds and cankers are two types of tree defects associated with hazards. Cankers are usually tree diseases that are perennial and aggressive. These defects enlarge with time and increase the likelihood of tree failure. Wounds and cankers can be weak points on a trunk and their position relative to the prevailing winds influences the risk they represent. A tree is more likely to break at a wound or canker if it is facing or opposite to the direction of the prevailing wind. Vertical cracks or seams along the trunk suggest internal defects.

A hollow tree is not necessarily a hazard tree. Cavities develop from bark wounds. Many old trees have large conspicuous cavities. Vigorous trees have been observed to grow more sound wood around the hollow, compensating for that lost to decay. Compartmentalization of the decay also prevents the size of the rotten compartment from expanding.

Inspect the Crown

Crown vigor and form are two indicators of the general health of trees. Crown characteristics of a potential hazard tree include dieback, V-shaped forks and lopsidedness. V-shaped forks are weak compared to broader angled forks and branches.

Branches in the upper crown often die from the top down in response to stress. Repeated insect defoliation, extended periods of drought, soil compaction and/or root disease can cause stress. Opportunistic pests, such as insects and fungi, often invade and further stress the tree. Trees can recover from dieback, if the source of the stress is eliminated in time. However, trees with advanced crown decline will die and should be removed.

Leaning, lopsided trees may represent a hazard if they are above a target. Generally, trees that lean more than 15 degrees from vertical should be removed. Trees that have grown leaning are not as hazardous as trees that were originally straight, but subsequently developed a lean due to wind or root damage. The general growth form of the tree and any uplifted soil on the side of the tree opposite the lean provide clues to when the lean developed.

Roots

Root integrity and health cannot be over emphasized. If the roots are damaged in any way, tree vitality and health are affected and the likelihood of failure increases. The probability of failure increases as the amount of the root damage increases. Above-ground clues to poor root conditions include thin crowns, dwarfed, off-color leaves, stunted growth, discolored or resin soaked wood at the root collar and fruiting bodies of root- rot fungi growing at or near the base of the trees.

What Can You Do?

Check your trees, especially large, old ones. Periodic, thorough inspections are essential to prevent accidents. Every tree likely to have a problem should be inspected from bottom to top, looking for signs of root or butt rot and continuing up the trunk toward the crown, noting anything that might indicate a potential hazard. At least one inspection per year should be made, but two per year are recommended, one in the summer while the leaves are on the tree and one in the winter.

Treatments

Since all trees are potential hazards, the only way to completely eliminate a tree hazard is to remove the tree. Where this is not acceptable, regular inspection and appropriate action is the best way to reduce your risks. Dead trees within the range of a target should be removed. When removing a hazard tree, prevent creating another hazard tree by limiting damage to the site and residual trees.

Prevention

Prevention is the best action. Start a tree health program as soon as possible. Proper selection and placement of trees prevents many hazard problems.

Summary

Hazard trees are unpredictable. They do not always fall when and where you think. Don't solve one problem just to create another. When in doubt contact your county AgriLife Extension agent or certified tree professional.

References

Harris, Richard W. 1992. Arboriculture: integrated management of landscape, trees, shrubs, and vines. 2nd ed., Prentice Hall, Inc. 674 p.

Johnson, David. 1981. Tree hazards: recognition and reduction in recreation sites. Technical Report R2-1. Lakewood, CO: USDA Forest Service, Forest Pest Management. 17 p.

Minnesota Dept.of Natural Resources and USDA Forest Service. 1996. How to recognize hazardous defects in trees. NA-FR-01-96. Radnor, PA: USDA Forest Service, Northeastern Area. 20 p.

Robbins, Kathryn. 1986. How to recognize and reduce tree hazards in recreation sites. USDA Forest Service NA-FR-31.

Sharon, E. Michael. 1987. Tree health management: evaluating trees for hazard. Journal of Arboriculture 13(12):285-293.

Tattar, Terry A. 1982. Living hazard-trees. Publication L-264, Cooperative Extension Service, Univ. of Massachusetts, Amherst.

###

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