What Your Tree Needs and Why
Why Hire An Arborist?
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.
Services That Arborists Can Provide
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
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 Tree 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.
Some arborists plant trees, and most can recommend types of trees that are appropriate for a specific location. The wrong tree in the wrong location could lead to future problems as a result of limited growing space, insects, diseases, or poor growth.
Many arborists also provide a variety of other tree care services, including:
- Plant Health Care, a concept of preventive maintenance to keep trees in good health, which will help the tree better defend itself against insects, disease, and site problems 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). Such membership demonstrates a willingness on the part of the arborist to stay up to date on the latest techniques and information.
- Check for ISA arborist certification. Certified Arborists are experienced professionals who have passed an extensive examination covering all aspects of tree care.
- 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. Many home owners have had to pay out large amounts of money for damages caused by uninsured individuals claiming to be tree experts. You could be held responsible for damages and injuries that occur as a result of the job.
- 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. Be sure they comply with any local, state, provincial, or national laws that govern their work.
- Ask for references to find out where the company has done work similar to the work you are requesting. Don’t hesitate to check references or visit other work sites where the company or individual has done tree work. Remember, tree care is a substantial, long-lasting investment; you would not buy a car without a test drive!
- 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. For example, practices such as topping a tree, removing an excessive amount of live wood, using climbing spikes on trees that are not being removed, and removing or disfiguring living trees without just cause are unnecessary.
- 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?
What Is a Certified Arborist?
An arborist by definition is an individual who is trained in the art and science of planting, caring for, and maintaining individual trees. ISA arborist certification is a nongovernmental, voluntary process by which individuals can document their base of knowledge. It operates without mandate of law and is an internal, self-regulating device administered by the International Society of Arboriculture. Certification provides a measurable assessment of an individual’s knowledge and competence required to provide proper tree care.
Certification is not a measure of standards of practice. Certification can attest to the tree knowledge of an individual but cannot guarantee or ensure quality performance. Certified Arborists are individuals who have achieved a level of knowledge in the art and science of tree care through experience and by passing a comprehensive examination developed by some of the nation’s leading experts on tree care. Certified Arborists must also continue their education to maintain their certification. Therefore, they are more likely to be up to date on the latest techniques in arboriculture.
Be an Informed Consumer
One of the best methods to use in choosing an arborist is to educate you 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.
Benefits of Trees
Most trees and shrubs in cities or communities are planted to provide beauty or 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 shrub for the landscape. The benefits of trees can be grouped into social, communal, environmental, and economic categories.
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. Hospital patients have been shown to recover from surgery more quickly when their hospital room offered a view of trees. 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.
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.
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.
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 non-landscaped homes. The savings in energy costs and the increase in property value directly benefit each home owner.
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 home owner. 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 garden center owner, university extension agent, 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. The 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.
What Are Your Trees Worth?
Almost everyone knows that trees and other living plants are valuable. They beautify our surroundings, purify our air, act as sound barriers, manufacture precious oxygen, and help us save energy through their cooling shade in summer and their wind reduction in winter.
Many people don’t realize, however, that plants have a dollar value of their own that can be measured by competent plant appraisers.
If your trees or shrubs are damaged or destroyed, you may be able to recapture your loss through an insurance claim or as a deduction from your federal income tax.
Some Practical Advice
Here is some practical advice that may help you find out what your trees and plants are worth (a process known as valuation).
Planning for Highest Value
A professional in the tree, nursery, or landscape industry can help you plan, develop, install, and care for all of your trees and plants so that each of them will be worth more to you.
How Your Trees and Shrubs Are Valuated
Seek the advice of professionals in this industry who have developed a set of guidelines for the valuation. Such guidelines have been widely adopted in the field and are recognized by insurance companies, the courts, and, in some cases, the Internal Revenue Service (IRS).
What to Do If You Suffer Loss or Damage to Your Landscape Plants
A casualty loss is defined by the IRS as “… a loss resulting from an identifiable event of sudden, unexpected, or unusual nature.” This definition can include such events as vehicular accidents, storms, floods, lightning, vandalism, or even air and soil pollution.
If you suffer damage to trees or landscaping from any type of casualty, first consult your home owner’s insurance policy to determine the amount and kind of coverage. Contact the insurance company to have an appraisal made by a competent tree and landscape professional who is experienced in plant appraisal. Have the appraisal made right after your loss or damage.
The tree and landscape appraiser accomplishes many things for you. The professional can see things you might miss, help correct damage, and prescribe remedies you may be able to do yourself. The appraiser will establish the amount of your loss in financial terms, including the cost of removing debris and making repairs as well as replacements. All of these steps are wise investments and well worth the cost you may incur for the inspection.
Four Factors in Professional Valuation of Trees and Other Plants
Size. Sometimes the size and age of a tree are such that it cannot be replaced. Trees that are too large to be replaced should be assessed by professionals who use a specialized appraisal formula.
Species or classification. Trees that are hardy, durable, highly adaptable, and free from objectionable characteristics are most valuable. They require less maintenance; they have sturdy, well-shaped branches, and pleasing foliage. Tree values vary according to your region, the “hardiness” zone, and even state and local conditions. If you are not familiar with these variables, be sure your advice comes from a competent source.
Condition. The professional will also consider the condition of the plant. Obviously, a healthy, well-maintained plant has a higher value. Roots, trunk, branches, and buds need to be inspected.
Location. Functional considerations are important. A tree in your yard may be worth more than one growing in the woods. A tree standing alone often has a higher value than one in a group. A tree near your house or one that is a focal point in your landscape tends to have more value. The site, placement, and contribution of a tree to the overall landscape help determine the overall value of the plant attributable to location.
All of these factors can be measured in dollars and cents. They can determine the value of a tree, specimen shrubs, or evergreens, whether for insurance purposes, court testimony in lawsuits, or tax deductions.
These steps should be taken before and after any casualty loss to your trees and landscape. Taking them can improve the value of your investment in nature’s green, growing gifts and prevent financial loss should they be damaged or destroyed.
- Plan your landscaping for both beauty and functional value.
- Protect and preserve to maintain value.
- Take pictures of trees and other landscape plants now while they are healthy and vigorous. Pictures make “before and after” comparisons easier and expedite the processing of insurance claims or deductions for losses on federal tax forms.
- Check your insurance. In most cases, the amount of an allowable claim for any one tree or shrub is a maximum of $500.
- For insurance, legal, and income tax purposes, keep accurate records of your landscape and real estate appraisals on any losses.
- Consult your local Plant Health Care professional at every stage in the life cycle of your landscape (planning, planting, care) and to make sure you do not suffer needless financial loss when a casualty strikes.
Before Tree Buying and Planting
Tree selection is one of the most important investment decisions a home owner makes when landscaping a new home or replacing a tree lost to damage or disease. Considering that most trees have the potential to outlive the people who plant them, the impact of this decision is one that can influence a lifetime. Match the tree to the site, and both lives will benefit.
The question most frequently asked of tree care professionals is “Which kind of tree do you think I should plant?” Before this question can be answered, a number of factors need to be considered. Think about the following questions:
- Why is the tree being planted? Do you want the tree to provide shade, fruit, or seasonal color, or act as a windbreak or screen? Maybe more than one reason?
- What is the size and location of the planting site? Does the space lend itself to a large, medium, or small tree? Are there overhead or belowground wires or utilities in the vicinity? Do you need to consider clearance for sidewalks, patios, or driveways? Are there other trees in the area?
- Which type of soil conditions exist? Is the soil deep, fertile, and well drained, or is it shallow, compacted, and infertile?
- Which type of maintenance are you willing to provide? Do you have time to water, fertilize, and prune the newly planted tree until it is established, or will you be relying on your garden or tree service for assistance?
- Asking and answering these and other questions before selecting a tree will help you choose the “right tree for the right place.”
Trees make our surroundings more pleasant. Properly placed and cared for, trees increase the value of our real estate. A large shade tree provides relief from summer’s heat and, when properly placed, can reduce summer cooling costs. An ornamental tree provides beautiful flowers, leaves, bark, or fruit. Evergreens with dense, persistent leaves can be used to provide a windbreak or a screen for privacy. A tree that drops its leaves in the fall allows the sun to warm a house in the winter. A tree or shrub that produces fruit can provide food for the owner and/or attract birds and wildlife into your home landscape. Street trees decrease the glare from pavement, reduce runoff, filter out pollutants, and add oxygen to the air we breathe. Street trees also improve the overall appearance and quality of life in a city or neighborhood.
Form and Size
A well-known quotation about architecture states, “Form follows function.” This is a good rule to remember when selecting a tree. Selecting the right form (shape) to complement the desired function (what you want the tree to do) can significantly reduce maintenance costs and increase the tree’s value in the landscape. When making a selection about form, also consider mature tree size. Trees grow in a variety of sizes and shapes, as shown below. They can vary in height from several inches to several hundred feet. Select a form and size that will fit the planting space provided.
Depending on your site restrictions, you can choose from among hundreds of combinations of form and size. You may choose a small-spreading tree in a location with overhead utility lines. You may select a narrow, columnar form to provide a screen between two buildings. You may choose large, vase-shaped trees to create an arbor over a driveway or city street. You may even determine that the site just does not have enough space for a tree of any kind.
Selecting a tree that will thrive in a given set of site conditions is the key to long-term tree survival. The following is a list of the major site conditions to consider before selecting a tree for planting:
- Soil conditions
- Exposure (sun and wind)
- Human activity
- Space constraints
- Hardiness zone
The amount and quality of soil present in your yard can limit planting success. In urban sites, the topsoil often has been disturbed and frequently is shallow, compacted, and subject to drought. Under these conditions, trees are continuously under stress. For species that are not able to handle these types of conditions, proper maintenance designed to reduce stress is necessary to ensure adequate growth and survival. Many arborists will, for a minor charge, take soil samples from your yard to test for fertility and pH (alkalinity or acidity). The tests will be returned with recommendations on ways to improve poor soil conditions with fertilizers or soil amendments (sand, peat moss, or manure) and will also help your local nursery or garden center recommend tree species that will do well in the soils found on your site.
The amount of sunlight available will affect tree and shrub species selection for a particular location. Most woody plants require full sunlight for proper growth and flower bloom. Some do well in light shade, but few tree species perform well in dense shade. Exposure to wind is also a consideration. Wind can dry out soils, causing drought conditions and damage to branches and leaves during storms, and can actually uproot newly planted trees that have not had an opportunity to establish root systems. Special maintenance, such as staking or more frequent watering, may be needed to establish young trees on windy sites.
This aspect of tree selection is often overlooked. The reality of the situation is that the top five causes of tree death are the result of things people do: soil compaction, under watering, over watering, vandalism, and the number one cause—planting the wrong tree—account for more tree deaths than all insect and disease-related tree deaths combined.
Tree roots require oxygen to develop and thrive. Poor drainage can remove the oxygen available to the roots from the soil and kill the tree. Before planting, dig some test holes 12 inches wide by 12 inches deep in the areas you are considering planting trees. Fill the holes with water and time how long it takes for the water to drain away. If it takes more than 6 hours, you may have a drainage problem. If so, ask your local garden center for recommendations on how to correct the problem, or choose a different site.
Many different factors can limit the planting space available to the tree: overhead or underground utilities, pavement, buildings, other trees, visibility. The list goes on and on. Make sure there is adequate room for the tree you select to grow to maturity, both above and below ground.
Hardiness is the plant’s ability to survive in the extreme temperatures of the particular geographic region in which you are planting the tree. Plants can be cold hardy, heat tolerant, or both. Most plant reference books provide a map of hardiness zone ranges. Check with your local garden center for the hardiness information for your region. Before you make your final decision, make sure the plant you have selected is “hardy” in your area.
Insect and disease organisms affect almost every tree and shrub species. Every plant has its particular pest problems, and the severity varies geographically. These pests may or may not be life threatening to the plant. You should select plants resistant to pest problems for your area. Your local ISA Certified Arborist, tree consultant, or extension agent can direct you to information relevant to problem species for your location.
Personal preferences play a major role in the selection process. Now that your homework is done, you are ready to select a species for the planting site you have chosen. Make sure you use the information you have gathered about your site conditions, and balance it with the aesthetic decisions you make related to your personal preferences.
The species must be suitable for the geographic region (hardy), tolerant to the moisture and drainage conditions of your soil, be resistant to pests in your area, and have the right form and size for the site and function you have envisioned.
Remember, the beautiful picture of a tree you looked at in a magazine or book was taken of a specimen that is growing vigorously because it was planted in the right place. If your site conditions tell you the species you selected will not do well under those conditions, do not be disappointed when the tree does not perform in the same way.
If you are having difficulty answering any of these questions on your own, contact a local ISA Certified Arborist, tree care professional, garden center, or extension agent for assistance. Their assistance will help you to plant the “right tree in the right place.” It is better to get a professional involved early and help you make the right decision than to call him or her later to ask if you made the wrong decision.
Buying High-Quality Trees
When you buy a high-quality tree, plant it correctly, and treat it properly, you and your tree will benefit greatly in many ways for many years.
When you buy a low-quality tree, you and your tree will have many costly problems even if you take great care in planting and maintenance.
What Determines Tree Quality?
A high-quality tree has:
- Enough sound roots to support healthy growth.
- A trunk free of mechanical wounds and wounds from incorrect pruning.
- A strong form with well-spaced, firmly attached branches.
A low-quality tree has:
- Crushed or circling roots in a small root ball or small container.
- A trunk with wounds from mechanical impacts or incorrect pruning.
- A weak form in which multiple stems squeeze against each other or branches squeeze against the trunk.
Any of these problems alone or in combination with the others will greatly reduce the tree’s chances for a long, attractive, healthy, and productive life.
When buying a tree, inspect it carefully to make certain it does not have problems with roots, injuries, or form. Remember the acronym RIF; it will help you remember roots, injuries, and form.
Here are some details on potential problems and some other considerations that you should be aware of when buying a tree.
Roots on trees for sale are available as one of three types:
- Bare root: no soil; usually on small trees
- Root balled: roots in soil held in place by burlap or some other fabric; the root ball may be in a wire basket
- Container grown: roots and soil in a container
Bare roots should not be crushed or torn. The ends of the roots should be clean cut. If a few roots are crushed, re-cut them to remove the injured portions. Use sharp tools. Make straight cuts. Do not paint the ends. The cuts should be made immediately before planting and watering.
You should be able to see the basal trunk flare. The flare is the spreading trunk base that connects with the roots. Root balls should be flat on top. Roots in soil in round bags often have many major woody roots cut or torn during the bagging process. Avoid trees with many crushed or torn roots.
The diameter of the root ball should be at least 10 to 12 times the diameter of the trunk as measured 6 inches above the trunk flare.
After placing the root ball in the planting site, cut the cords and carefully pull away the burlap or other fabric. Examine any roots that protrude from the soil. If many roots are obviously crushed or torn, the tree will have severe growth problems. If only a few roots are injured, cut away only the injured portions. Use a sharp tool. Use care not to break the soil ball around the roots.
Cut the wire on wire baskets. Place the basket into the planting site. Cut away at least the top two wires without disturbing the root ball. Inspect exposed roots for injuries. If many roots are injured, the tree may have serious growth problems.
Roots should not twist or circle in the container. Remove the root ball from the container. Inspect the exposed larger roots carefully to see whether they are twisting or turning in circles. Circling roots often girdle and kill other roots. If only a few roots are circling, cut them away with a sharp tool.
Trunk flare should be obvious. Be on alert for trees planted too deeply in containers or trees “buried” in fabric bags. As with root-balled stock, you should be able to see the basal trunk flare with container-grown plants.
Beware of injuries beneath trunk wraps. Never buy a tree without thoroughly checking the trunk. If the tree is wrapped, remove the wrap and inspect the trunk for wounds, incorrect pruning cuts, and insect injuries. Wrap can be used to protect the trunk during transit but should be removed after planting.
Incorrect pruning cuts are major problems. Incorrect pruning cuts that remove or injure the swollen collar at the base of branches can start many serious tree problems, cankers, decay, and cracks.
Incorrect pruning cuts that leave branch and leader stubs also start disease and defect problems. Do not leave stubs.
A correct pruning cut removes the branch just outside of the collar. A ring, or “doughnut,” of sound tissues then grows around the cut. Do not make cuts flush to the trunk. The closing tissues may form only to the sides of the flush cuts. Trunk tissues above and below flush cut branches often die. When the heat of the sun or the cold of frost occurs, cracks or long, dead streaks may develop above and below the dead spots.
Good, strong form, or architecture, starts with branches evenly spaced along the trunk. The branches should have firm, strong attachments with the trunk.
Squeezed branches signal problems. Weak branch unions occur where the branch and trunk squeeze together. As the squeezing increases during diameter growth, dead spots or cracks often begin to form below where the branch is attached to the trunk. Once this problem starts, the weak branch attachment could lead to branches cracking or breaking during mild to moderate storms.
When several branches are on the same position on the trunk, the likelihood of weak attachments and cracks increases greatly. As the branches grow larger and tighter together, the chances for splitting increase.
Avoid trees with two or more stems squeezing together. As stems squeeze together, cracks often form down the trunk. The cracks could start from squeezed multiple leader stems or where the two trunks come together.
If you desire a tree with multiple trunks, such as a birch clump, make certain that the trunks are well separated at the ground line.
Remember, trunks expand in diameter as they grow. Two trunks may be slightly separated when small, but as they grow in girth, the trunks will squeeze together.
Look for early signs of vertical trunk cracks. Examine branch unions carefully for small cracks below the unions. Cracks are major starting points for fractures of branches and trunks. The small cracks could be present for many years before a fracture happens. Always keep a close watch for vertical cracks below squeezed branches and squeezed trunks.
If your tree has only a few minor problems, corrective pruning may help. Start corrective pruning one year after planting. Space the pruning over several years.
Remove broken or torn branches at the time of planting. After a year, start corrective pruning by removing the branches that died after planting.
Trees Have Dignity, Too
Most nurseries produce high-quality trees. When you start with a high-quality tree, you are giving that tree a chance to express its dignity for many years. Remember RIF.
Avoiding Tree & Utility Conflicts
Determining where to plant a tree is a decision that should not be taken lightly. Many factors should be considered prior to planting. When planning what type of tree to plant, remember to look up and look down to determine where the tree will be located in relation to overhead and underground utility lines.
Often, we take utility services for granted because they have become a part of our daily lives. For us to enjoy the convenience of reliable, uninterrupted service, distribution systems are required to bring utilities into our homes. These services arrive at our homes through overhead or underground lines.
Overhead lines can be electric, telephone, or cable television. Underground lines include those three plus water, sewer, and natural gas.
The location of these lines should have a direct impact on your tree and planting site selection. The ultimate mature height of a tree to be planted must be within the available overhead growing space. Just as important, the soil area must be large enough to accommodate the particular rooting habits and ultimate trunk diameter of the tree. Proper tree and site selection provide trouble-free beauty and pleasure for years to come.
Overhead utility lines are the easiest to see and probably the ones we take most for granted. Although these lines look harmless enough, they can be extremely dangerous.
Planting tall-growing trees under and near these lines eventually requires your utility to prune them to maintain safe clearance from the wires. This pruning may result in the tree having an unnatural appearance.
Periodic pruning can also lead to a shortened life span for the tree. Trees that must be pruned away from power lines are under greater stress and are more susceptible to insects and disease. Small, immature trees planted today can become problem trees in the future.
Tall-growing trees near overhead lines can cause service interruptions when trees contact wires. Children or adults climbing in these trees can be severely injured or even killed if they come in contact with the wires. Proper selection and placement of trees in and around overhead utilities can eliminate potential public safety hazards, reduce expenses for utilities and their rate payers, and improve the appearance of landscapes.
Trees are much more than just what you see overhead. Many times, the root area is larger than the branch spread above ground. Much of the utility service provided today runs below ground. Tree roots and underground lines often coexist without problems. However, trees planted near underground lines could have their roots damaged if the lines need to be dug up for repairs.
The biggest danger to underground lines occurs during planting. Before you plant, make sure that you are aware of the location of any underground utilities. To be certain that you do not accidentally dig into any lines and risk serious injury or a costly service interruption, call your utility company or utility protection service first. Never assume that these utility lines are buried deeper than you plan to dig. In some cases, utility lines are very close to the surface.
Proper Places for Trees Around Homes
The illustration indicates approximately where trees should be planted in relation to utility lines. Your garden center staff or tree care professional will gladly help you select the right tree.
Trees that grow as tall as 60 feet (20 meters) can be used in the area marked as the tall zone; however, you should consider your neighbor’s view or their existing plantings of flower beds and/or trees.
Plant large trees at least 35 feet (11 meters) away from the house for proper root development and to minimize damage to the house or building. These large-growing trees are also recommended for streets without overhead restrictions.
Street planting sites must also have wide planting areas or medians [greater than 8 feet (3 meters)] that allow for a large root system, trunk diameter, and root flare.
Large trees are also recommended for parks, meadows, or other open areas where their large size, both above and below ground, will not be restricted, cause damage or become a liability.
Trees that grow up to 40 feet (12 meters) tall can be used to decorate or frame your house or provide a park like setting. Select your trees first, then plant shrubs to complement the trees. Medium-sized trees are also recommended for planting anywhere the available above and below ground growing space will allow them to reach a mature height of 30 to 40 feet (10 to 12 meters). Appropriate soil spaces are wide planting areas or medians [4 to 8 feet (1 to 3 meters) wide], large planting squares [8 feet (3 meters) square or greater], and other open areas of similar size or larger.
This zone extends 15 feet (4.5 meters) on either side of the wires. Trees with a mature height of less than 20 feet (6 meters) may be planted anywhere within this zone, including street tree plantings under utility lines. Such trees are also recommended when the growing space is limited. These trees are appropriate as well for narrow planting areas [less than 4 feet (1 meter) wide]; planting squares or circles surrounded by concrete; large, raised planting containers; or other locations where underground space for roots will not support tall- or medium-zone trees.
Some Further Suggestions
Plant evergreen trees to serve as windbreaks on the west or north side of the house, approximately 50 feet (15 meters) or more from the house.
Plant deciduous trees (those that drop their leaves in the fall) on the south and/or west side of the house to cool in the summer and allow sun to enter the house in the winter.
Right Tree—Right Place
Planning before planting can help ensure that the right tree is planted in the right place. Proper tree selection and placement enhance your property value and prevent costly maintenance trimming and damage to your home. For further information on planting and helpful tips on tree selection, refer to ISA’s brochures on tree selection and new tree planting. If you have any more questions, please contact your local ISA Certified Arborist or tree care professional, utility company, local nursery, or county extension office.
New Tree Planting
Think of the tree you just purchased as a lifetime investment. How well your tree, and investment, grows depends on the type of tree and location you select for planting, the care you provide when the tree is planted, and follow-up care the tree receives after planting.
Planting the Tree
The ideal time to plant trees and shrubs is during the dormant season—in the fall after leaf drop or early spring before bud break. Weather conditions are cool and allow plants to establish roots in the new location before spring rains and summer heat stimulate new top growth. However, trees properly cared for in the nursery or garden center, and given the appropriate care during transport to prevent damage, can be planted throughout the growing season. In either situation, proper handling during planting is essential to ensure a healthy future for new trees and shrubs. Before you begin planting your tree, be sure you have had all underground utilities located prior to digging.
Whether the tree you are planting is balled and burlapped or is bare root, it is important to understand that its root system has been reduced by 90 to 95 percent of its original size during transplanting. As a result of the trauma caused by the digging process, trees commonly exhibit what is known as transplant shock. Transplant shock is indicated by slow growth and reduced vigor following transplanting. Proper site preparation before and during planting coupled with good follow-up care reduces the amount of time the plant experiences transplant shock and allows the tree to quickly establish in its new location. Carefully follow eight simple steps, and you can significantly reduce the stress placed on the plant at the time of planting.
Dig a shallow, broad planting hole. Make the hole wide, as much as three times the diameter of the root ball but only as deep as the root ball. It is important to make the hole wide because the roots on the newly establishing tree must push through surrounding soil in order to establish. On most planting sites in new developments, the existing soils have been compacted and are unsuitable for healthy root growth. Breaking up the soil in a large area around the tree provides the newly emerging roots room to expand into loose soil to hasten establishment.
Identify the trunk flare. The trunk flare is where the roots spread at the base of the tree. This point should be partially visible after the tree has been planted (see diagram). If the trunk flare is not partially visible, you may have to remove some soil from the top of the root ball. Find it so you can determine how deep the hole needs to be for proper planting.
Place the tree at the proper height. Before placing the tree in the hole, check to see that the hole has been dug to the proper depth—and no more. The majority of the roots on the newly planted tree will develop in the top 12 inches of soil. If the tree is planted too deeply, new roots will have difficulty developing because of a lack of oxygen. It is better to plant the tree a little high, 2 to 3 inches above the base of the trunk flare, than to plant it at or below the original growing level. This planting level will allow for some settling (see diagram). To avoid damage when setting the tree in the hole, always lift the tree by the root ball and never by the trunk.
Straighten the tree in the hole. Before you begin backfilling, have someone view the tree from several directions to confirm that the tree is straight. Once you begin backfilling, it is difficult to reposition the tree.
Fill the hole gently but firmly. Fill the hole about one-third full and gently but firmly pack the soil around the base of the root ball. Then, if the tree is balled and burlapped, cut and remove the string and wire from around the trunk and top third of the root ball (see diagram). Be careful not to damage the trunk or roots in the process.
Fill the remainder of the hole, taking care to firmly pack soil to eliminate air pockets that may cause roots to dry out. To avoid this problem, add the soil a few inches at a time and settle with water. Continue this process until the hole is filled and the tree is firmly planted. It is not recommended to apply fertilizer at the time of planting.
Stake the tree, if necessary. If the tree is grown and dug properly at the nursery, staking for support will not be necessary in most home landscape situations. Studies have shown that trees establish more quickly and develop stronger trunk and root systems if they are not staked at the time of planting. However, protective staking may be required on sites where lawn mower damage, vandalism, or windy conditions are concerns. If staking is necessary for support, there are three methods to choose among: staking, guying, and ball stabilizing. One of the most common methods is staking. With this method, two stakes used in conjunction with a wide, flexible tie material will hold the tree upright, provide flexibility, and minimize injury to the trunk (see diagram). Remove support staking and ties after the first year of growth.
Mulch the base of the tree. Mulch is simply organic matter applied to the area at the base of the tree. It acts as a blanket to hold moisture, it moderates soil temperature extremes (both hot and cold), and it reduces competition from grass and weeds. Some good choices are leaf litter, pine straw, shredded bark, peat moss, or wood chips. A 2- to 4-inch layer is ideal. More than 4 inches may cause a problem with oxygen and moisture levels. When placing mulch, be sure that the actual trunk of the tree is not covered. Doing so may cause decay of the living bark at the base of the tree. A mulch-free area, 1 to 2 inches wide at the base of the tree, is sufficient to avoid moist bark conditions and prevent decay.
Provide follow-up care. Keep the soil moist but not soaked; over watering causes leaves to turn yellow or fall off. Water trees at least once a week, barring rain, and more frequently during hot weather. When the soil is dry below the surface of the mulch, it is time to water. Continue until mid-fall, tapering off for lower temperatures that require less-frequent watering.
Other follow-up care may include minor pruning of branches damaged during the planting process. Prune sparingly immediately after planting and wait to begin necessary corrective pruning until after a full season of growth in the new location.
After you’ve completed these eight simple steps, further routine care and favorable weather conditions will ensure that your new tree or shrub will grow and thrive. A valuable asset to any landscape, trees provide a long-lasting source of beauty and enjoyment for people of all ages. When questions arise about the care of your tree, be sure to consult your local ISA Certified Arborist or a tree care or garden center professional for assistance.
The PHC Alternative
Maintaining mature landscapes is a complicated undertaking. You may wish to consider a professional Plant Health Care (PHC) maintenance program, which is now available from many landscape care companies. A PHC program is designed to maintain plant vigor and should initially include inspections to detect and treat any existing problems that could be damaging or fatal. Thereafter, regular inspections and preventive maintenance will ensure plant health and beauty.
Proper Tree Care Techniques
Mature Tree Care
Think of tree care as an investment. A healthy tree increases in value with age—paying big dividends, increasing property values, beautifying our surroundings, purifying our air, and saving energy by providing cooling shade from summer’s heat and protection from winter’s wind.
Providing a preventive care program for your landscape plants is like putting money in the bank. Regular maintenance, designed to promote plant health and vigor, ensures their value will continue to grow. Preventing a problem is much less costly and time-consuming than curing one once it has developed. An effective maintenance program, including regular inspections and the necessary follow-up care of mulching, fertilizing, and pruning, can detect problems and correct them before they become damaging or fatal. Considering that many tree species can live as long as 200 to 300 years, including these practices when caring for your home landscape is an investment that will offer enjoyment and value for generations.
Tree inspection is an evaluation tool to call attention to any change in the tree’s health before the problem becomes too serious. By providing regular inspections of mature trees at least once a year, you can prevent or reduce the severity of future disease, insect, and environmental problems. During tree inspection, be sure to examine four characteristics of tree vigor: new leaves or buds, leaf size, twig growth, and absence of crown dieback (gradual death of the upper part of the tree).
A reduction in the extension of shoots (new growing parts), such as buds or new leaves, is a fairly reliable cue that the tree’s health has recently changed. To evaluate this factor, compare the growth of the shoots over the past three years. Determine whether there is a reduction in the tree’s typical growth pattern.
Further signs of poor tree health are trunk decay, crown dieback, or both. These symptoms often indicate problems that began several years before. Loose bark or deformed growths, such as trunk conks (mushrooms), are common signs of stem decay.
Any abnormalities found during these inspections, including insect activity and spotted, deformed, discolored, or dead leaves and twigs, should be noted and watched closely. If you are uncertain as to what should be done, report your findings to your local ISA Certified Arborist or other tree care professional for advice on possible treatment.
Mulching can reduce environmental stress by providing trees with a stable root environment that is cooler and contains more moisture than the surrounding soil. Mulch can also prevent mechanical damage by keeping machines such as lawn mowers and string trimmers away from the tree’s base. Further, mulch reduces competition from surrounding weeds and turf.
To be most effective in all of these functions, mulch should be placed 2 to 4 inches deep and cover the entire root system, which may be as far as 2 or 3 times the diameter of the branch spread of the tree. If the area and activities happening around the tree do not permit the entire area to be mulched, it is recommended that you mulch as much of the area under the drip line of the tree as possible (refer to diagram). When placing mulch, care should be taken not to cover the actual trunk of the tree. This mulch-free area, 1 to 2 inches wide at the base, is sufficient to avoid moist bark conditions and prevent trunk decay.
An organic mulch layer 2 to 4 inches deep of loosely packed shredded leaves, pine straw, peat moss, or composted wood chips is adequate. Plastic should not be used because it interferes with the exchange of gases between soil and air, which inhibits root growth. Thicker mulch layers, 5 to 6 inches deep or greater, may also inhibit gas exchange.
Fertilization is another important aspect of mature tree care. Trees require certain nutrients (essential elements) to function and grow. Urban landscape trees can be growing in soils that do not contain sufficient available nutrients for satisfactory growth and development. In these situations, it may be necessary to fertilize to improve plant vigor.
Fertilizing a tree can improve growth; however, if fertilizer is not applied wisely, it may not benefit the tree at all and may even adversely affect the tree. Mature trees making satisfactory growth may not require fertilization. When considering supplemental fertilizer, it is important to know which nutrients are needed and when and how they should be applied.
Soil conditions, especially pH and organic matter content, vary greatly, making the proper selection and use of fertilizer a somewhat complex process. When dealing with a mature tree that provides considerable benefit and value to your landscape, it is worth the time and investment to have the soil tested for nutrient content. Any arborist can arrange to have your soil tested at a soil testing laboratory and can give advice on application rates, timing, and the best blend of fertilizer for each of your trees and other landscape plants.
Mature trees have expansive root systems that extend from 2 to 3 times the size of the leaf canopy. A major portion of actively growing roots is located outside the tree’s drip line. It is important to understand this fact when applying fertilizer to your trees as well as your turf. Many lawn fertilizers contain weed and feed formulations that may be harmful to your trees. When you apply a broadleaf herbicide to your turf, remember that tree roots coexist with turf roots. The same herbicide that kills broadleaf weeds in your lawn is picked up by tree roots and can harm or kill your broadleaf trees if applied incorrectly. Understanding the actual size and extent of a tree’s root system before you fertilize is necessary to determine how much, what type, and where to best apply fertilizer.
Pruning is the most common tree maintenance procedure next to watering. Pruning is often desirable or necessary to remove dead, diseased, or insect-infested branches and to improve tree structure, enhance vigor, or maintain safety. Because each cut has the potential to change the growth of (or cause damage to) a tree, no branch should be removed without a reason.
Removing foliage from a tree has two distinct effects on its growth. Removing leaves reduces photosynthesis and may reduce overall growth. That is why pruning should always be performed sparingly. Overpruning is extremely harmful because without enough leaves, a tree cannot gather and process enough sunlight to survive. However, after pruning, the growth that does occur takes place on fewer shoots, so they tend to grow longer than they would without pruning. Understanding how the tree responds to pruning should assist you when selecting branches for removal.
Pruning mature trees may require special equipment, training, and experience. If the pruning work requires climbing, the use of a chain or hand saw, or the removal of large limbs, then using personal safety equipment, such as protective eyewear and hearing protection, is a must. Arborists can provide a variety of services to assist in performing the job safely and reducing risk of personal injury and damage to your property. They also are able to determine which type of pruning is necessary to maintain or improve the health, appearance, and safety of your trees.
Although tree removal is a last resort, there are circumstances when it is necessary. An arborist can help decide whether or not a tree should be removed. Professionally trained arborists have the skills and equipment to safely and efficiently remove trees. Removal is recommended when a tree:
- Is dead, dying, or considered irreparably hazardous
- Is causing an obstruction or is crowding and causing harm to other trees and the situation is impossible to correct through pruning
- Is to be replaced by a more suitable specimen
- Should be removed to allow for construction
With proper maintenance, trees are attractive and can add considerable value to your property. Poorly maintained trees, on the other hand, can be a significant liability. Pruning or removing trees, especially large trees, can be dangerous work. It should be performed only by those trained and equipped to work safely in trees. For more information on mature tree care, contact your local ISA Certified Arborist.
The PHC Alternative
Maintaining mature landscapes is a complicated undertaking. You may wish to consider a professional Plant Health Care (PHC) maintenance program, which is now available from many landscape care companies. A PHC program is designed to maintain plant vigor and should initially include inspections to detect and treat any existing problems that could be damaging or fatal. Thereafter, regular inspections and preventive maintenance will ensure plant health and beauty.
Plant Health Care
The most common reason a tree owner calls an arborist is concern that something is wrong with a tree. It may be that some of the leaves are discolored, a branch has died, or perhaps the entire tree has been dropping leaves. Sometimes the cause of concern is a minor problem that is easily explained and corrected. Other times the problem is more complex—with several underlying causes and a remedy that requires treatments extending over several years. Unfortunately, there are instances in which the problem has gone undetected for so long that the tree cannot be helped, and the only option is removal. If an arborist had been called earlier, perhaps the tree could have been saved.
The Solution: Plant Health Care
Situations such as these led arborists to create Plant Health Care (PHC) programs. The objective of PHC is to maintain or improve the landscape’s appearance, vitality and—in the case of trees—safety, using the most cost-effective and environmentally sensitive practices and treatments available. Plant Health Care involves monitoring, using preventive treatments, and adopting a strong commitment to working closely with you, the tree owner.
Why Plant Health Care, Not Tree Health Care?
While trees are dominant ornamental features in your home landscape, they share this area with turfgrasses, shrubs, and bedding plants. And all these plants have one resource in common: the soil. The roots of trees, shrubs, turf grass, and bedding plants intermingle and compete for water and nutrients. In fact, the roots of a single mature tree may extend 60 feet or more out into your lawn or flower beds. Every treatment applied to the lawn (fertilizer and herbicide, for example) can impact the appearance and vitality of a tree. Conversely, treatments applied to a tree, such as pruning and fertilizing, can influence the appearance and vitality of the underlying turf grass. The care of each plant in a landscape can affect the health of every plant in that landscape.
Why Contact an Arborist for Plant Health Care?
Trees and shrubs represent a considerable long-term investment in your landscape. With proper care, these plants can provide beautiful surroundings, cooling shade, and many other benefits for decades. Arborists have the experience and training to detect many potential tree and shrub problems before they become life threatening or hazardous. In addition, arborists can make tree and shrub recommendations, such as species selection and placement, to keep many problems from occurring in the first place. Arborists can also consult with other landscape services you may use, lawn care for example, to ensure that the treatments are coordinated and will not be harmful to your trees and shrubs. Remember, the potential size and longevity of trees and shrubs warrants their special attention in your landscape. Bedding plants can be replaced in a few short weeks and a lawn in a single growing season, but it can take a lifetime or more to replace a mature tree.
What Does a Tree and Shrub PHC Program Cover?
Every home landscape is unique, so there is no standard PHC program. Plant Health Care programs do have features in common, however. First, PHC involves monitoring tree and shrub health. This step allows problems to be detected and managed before they become serious. The monitoring may be as simple as annual visits to check on a few special trees in your landscape, or it may involve more frequent quarterly or monthly inspections of all your trees and shrubs. The monitoring frequency and complexity of your PHC program depend on the size and diversity of your landscape as well as your particular landscape goals.
Second, if problems or potential problems are detected or anticipated during a monitoring visit, your arborist will develop solutions. The solution could be a simple change in your lawn irrigation schedule—many trees are kept too moist—or more detailed suggestions, such as pruning or spot applications of pesticides.
Finally, PHC involves you, the client. Your arborist will give you information about your trees and shrubs. This information ensures that decisions are made that address your concerns and are appropriate to your landscape budget and goals. Information may be provided through a variety of means. Obviously, discussions and answering questions are important means of conveying information, but many PHC programs include written recommendations after each monitoring visit. Plant Health Care is a program tailored to the needs of the client and his or her trees and shrubs.
How Will My Trees and Shrubs Benefit from PHC?
Because ornamental trees and shrubs can quickly succumb to problems, routine monitoring and timely treatments can protect your landscape investment and reduce expenses. A monitoring visit to your landscape might reveal:
- A hidden infestation of tent caterpillars that may soon defoliate the ornamental crabapples in your front yard
- A weakly attached branch that may fail and damage the house
- Improperly pruned shrubs that are not flowering as abundantly as they should.
Your Plant Health Care specialist can recommend treatments and changes in maintenance practices that can eliminate these problems while maximizing the safety and aesthetic quality of your landscape.
What Will a PHC Program Cost?
Because each program is individually designed to fit the needs of a particular landscape, no standard price can be given without a site visit and assessment. You may have an interest in developing a plan for a few key trees in your landscape, or you may wish to have the entire landscape placed on a program. PHC programs can also be structured in different ways. For example, some programs charge a fee for monitoring and bill each treatment separately. Other programs have an annual fee that covers all monitoring visits for the season as well as many potential treatments. These more comprehensive programs provide the peace of mind in knowing that treatments for most potential problems are already covered by the program without additional charges. Individualized programs and flexibility are at the heart of PHC. You will find that your arborist can design a Plant Health Care program that fits your goals and budget.
How Do I Choose an Arborist?
Check the phone directory for arborists who are members of professional organizations such as the International Society of Arboriculture (ISA), the Tree Care Industry Association (TCIA), or the American Society of Consulting Arborists (ASCA), and also look for ISA Certified Arborists. These credentials demonstrate a commitment to education and to staying abreast of the latest information and techniques. Ask for proof of insurance and references, and don’t hesitate to check them. Remember, tree care is a substantial, long-lasting investment in your valuable assets; take the time to select a knowledgeable professional to care for your landscape.
Trees and Turf
Woody plants and turf grasses are critical components of design plans for homes, offices, and parks. Trees and turf offer distinct personal, functional, and environmental benefits. Personal preferences for color, fragrance, and form should complement the functional properties of size, shape, density, and placement of plant material.
We’ve all seen thinning grass under large shade trees, large surface tree roots that cause safety hazards and mowing obstacles, young trees that don’t seem to grow, and tree trunks badly damaged by lawn mowers or string trimmers. All of these undesirable effects can be caused by trees and turf growing too closely together.
Turf grasses provide many of the same environmental benefits as trees. They:
- Change carbon dioxide into the oxygen we breathe
- Cool the air by changing water into water vapor
- Stabilize dust
- Entrap air polluting gases
- Control erosion
Turf grasses, in addition to being environmentally beneficial, are attractive in formal and informal designs. There are many advantages to combining trees and turf in the landscape.
When trees and turf are used in the same areas, extra attention must be given to plant material selection in addition to the usual hardiness, climatic, and soil needs. An effort should be made to make the trees and lawn compatible. Grass is generally a sun-loving plant. Most grass species will not grow well in areas that get less than 50 percent open sunlight; however, new varieties with improved shade tolerance are being introduced. Consult your garden center specialist or sod producer for recommendations of shade-tolerant grasses for your area.
In areas where the lawn is the primary design feature, select woody plants that do the least damage to grass growth and maintenance. The woody plants should be small, have an open canopy (to allow sunlight to penetrate to the ground), or have a high canopy. Select trees that do not root near the soil surface; surface rooting is most serious where shallow topsoil is present. Remember, tree roots get larger as the tree gets older.
Trees, shrubs, ground covers, and lawn grasses all require sunlight, water, and rooting space for growth. Each plant in the landscape competes with neighboring plants regardless of type or species. Some even produce chemicals that are exuded from roots to restrict growth of nearby plants. For each plant to do well, it must have adequate space. Because perennial woody plants increase in size each year, they require additional space over time. The landscape design should provide adequate space for these plants to mature.
While shade is the biggest, most obvious problem trees create for turf growth, a tree’s roots also contribute to poor turf performance. Contrary to general thinking, most tree roots are in the top 2 feet of soil. More important, the majority of fine, water absorbing roots is in the top 6 inches of soil. Grass roots ordinarily occupy a much greater percentage of the soil volume than tree roots and they out-compete them for water and nutrients, especially around young trees. However, grass root density is often much lower in areas where trees were established first. In these situations, tree roots compete much better for water and nutrients and prevent or reduce the success of establishing new turf.
Competition is especially important when transplanting, seeding, or sodding. The newest plant in the area must be given special treatment and must receive adequate water, nutrients, and sunlight, which frequently means that competing sod should be removed from around transplanted trees and shrubs or that some of the lower branches should be removed from existing trees above a newly sodded lawn. In any case, do not do any tilling around trees.
Mulching is an alternative to turf around trees, and its use eliminates potential competition. A 2- to 4-inch layer of wood chips, bark, or other organic material over the soil under the drip line is recommended because it:
- Helps retain soil moisture
- Helps reduce weeds and controls grass
- Increases soil fertility when mulch decomposes
- Improves appearance
- Protects the trunk from injuries caused by mowing equipment and trimmers that often result in serious tree damage or death
- Improves soil structure (better aeration, temperature, and moisture conditions)
Maintenance practices for trees and turf are different, and treatment of one can unintentionally damage the other. Because tree and grass roots exist together in the upper 6 to 8 inches of the topsoil, treatment of one may damage the other. Fertilizer applied to one plant will also be absorbed by the roots of a nearby plant. Normally that is good, but excessive fertilization of either trees or turf can result in tree crown or grass blade growth greater than desired.
Many herbicides or weed killers that are used in turf can cause severe damage to trees when misapplied. Misapplication can occur on windy days, causing the drift to fall on non-target plants, or on hot days when the herbicide may vaporize and diffuse into the air. While most herbicides do not kill tree roots, some, such as soil sterilants and a few others, do. Herbicides that can cause tree damage have statements on their labels warning against using the product near trees.
Watering of lawns is beneficial to trees if the watering is done correctly. Trees need the equivalent of one inch of rain every seven to ten days. Frequent, shallow watering does not properly meet the needs of either trees or turf and can be harmful to both.
Turf growing under or near trees should be mowed at the top of its recommended mowing height. Mowing off no more than one-third of the grass blade’s height and letting the clippings remain on the lawn does much to ensure a healthy and vigorous lawn. In an ideal situation, tree and turf maintenance would be handled by the same individual in order to maximize the benefits of all maintenance practices.
- Placing fill dirt around existing trees. Fill dirt frequently is added around existing mature trees so that a level or more visually desirable lawn can be established. Fill dirt changes the ratio of oxygen to carbon dioxide around tree roots and the roots may subsequently die. Consult a tree care expert before adding fill or constructing soil wells around tree trunks.
- Establishing lawns around existing trees. Preparation of a seedbed for lawns requires disruption of the upper 4 to 6 inches of topsoil. This soil contains the feeder roots of trees. Damage to tree roots often results in declining tree tops.
- Creating tree root buffers with turf. A sufficiently wide strip of turf grass between trees and hard surfaces such as building foundations, sidewalks, and roads can help to reduce the potential damage caused by tree roots as well as provide an area where water and nutrients can soak into the soil and be beneficial to both turf and trees.
- Lawn watering in arid sites. Homes are sometimes built in woodlots. In arid regions, the watering that is required to maintain grass is especially damaging to dry land trees. Excess water at the tree trunk encourages growth of fungi that can kill trees.
Thin turf grass growing around trunk-scarred weak trees does not need to be a common sight in the landscape. With proper planning, proper plant selection and placement, and reasonable management, the many and varied benefits of both trees and turf can be readily achieved.
Proper Mulching Techniques
Mulches are materials placed over the soil surface to maintain moisture and improve soil conditions. Mulching is one of the most beneficial things a home owner can do for the health of a tree. Mulch can reduce water loss from the soil, minimize weed competition, and improve soil structure. Properly applied, mulch can give landscapes a handsome, well-groomed appearance. Mulch must be applied properly; if it is too deep or if the wrong material is used, it can actually cause significant harm to trees and other landscape plants.
Benefits of Proper Mulching
- Helps maintain soil moisture. Evaporation is reduced, and the need for watering can be minimized.
- Helps control weeds. A 2- to 4-inch layer of mulch will reduce the germination and growth of weeds.
- Mulch serves as nature’s insulating blanket. Mulch keeps soils warmer in the winter and cooler in the summer.
- Many types of mulch can improve soil aeration, structure (aggregation of soil particles), and drainage over time.
- Some mulch can improve soil fertility.
- A layer of mulch can inhibit certain plant diseases.
- Mulching around trees helps facilitate maintenance and can reduce the likelihood of damage from “weed whackers” or the dreaded “lawn mower blight.”
- Mulch can give planting beds a uniform, well-cared-for look.
Trees growing in a natural forest environment have their roots anchored in a rich, well-aerated soil full of essential nutrients. The soil is blanketed by leaves and organic materials that replenish nutrients and provide an optimal environment for root growth and mineral uptake. Urban landscapes, however, are typically a much harsher environment with poor soils, little organic matter, and large fluctuations in temperature and moisture. Applying a 2- to 4-inch layer of organic mulch can mimic a more natural environment and improve plant health.
The root system of a tree is not a mirror image of the top. The roots of most trees can extend out a significant distance from the tree trunk. Although the guideline for many maintenance practices is the drip line—the outermost extension of the canopy—the roots can grow many times that distance. In addition, most of the fine, absorbing roots is located within inches of the soil surface. These roots, which are essential for taking up water and minerals, require oxygen to survive. A thin layer of mulch, applied as broadly as practical, can improve the soil structure, oxygen levels, temperature, and moisture availability where these roots grow.
Types of Mulch
Mulches are available commercially in many forms. The two major types of mulch are inorganic and organic. Inorganic mulches include various types of stone, lava rock, pulverized rubber, geotextile fabrics, and other materials. Inorganic mulches do not decompose and do not need to be replenished often. On the other hand, they do not improve soil structure, add organic materials, or provide nutrients. For these reasons, most horticulturists and arborists prefer organic mulches.
Organic mulches include wood chips, pine needles, hardwood and softwood bark, cocoa hulls, leaves, compost mixes, and a variety of other products usually derived from plants. Organic mulches decompose in the landscape at different rates depending on the material. Those that decompose faster must be replenished more often. Because the decomposition process improves soil quality and fertility, many arborists and other landscape professionals consider that characteristic a positive one, despite the added maintenance.
Not Too Much!
As beneficial as mulch is, too much can be harmful. The generally recommended mulching depth is 2 to 4 inches. Unfortunately, North American landscapes are falling victim to a plague of over-mulching. A new term, “mulch volcanoes,” has emerged to describe mulch that has been piled up around the base of trees. Most organic mulches must be replenished, but the rate of decomposition varies. Some mulches, such as cypress mulch, remain intact for many years. Top dressing with new mulch annually (often for the sake of refreshing the color) creates a buildup to depths that can be unhealthy. Deep mulch can be effective in suppressing weeds and reducing maintenance, but it often causes additional problems.
Problems Associated with Improper Mulching
- Deep mulch can lead to excess moisture in the root zone, which can stress the plant and cause root rot.
- Piling mulch against the trunk or stems of plants can stress stem tissues and may lead to insect and disease problems.
- Some mulch, especially those containing cut grass, can affect soil pH. Continued use of certain mulches over long periods can lead to micronutrient deficiencies or toxicities.
- Mulch piled high against the trunks of young trees may create habitats for rodents that chew the bark and can girdle the trees.
- Thick blankets of fine mulch can become matted and may prevent the penetration of water and air. In addition, a thick layer of fine mulch can become like potting soil and may support weed growth.
- Anaerobic “sour” mulch may give off pungent odors, and the alcohols and organic acids that build up may be toxic to young plants.
It is clear that the choice of mulch and the method of application can be important to the health of landscape plants. The following are some guidelines to use when applying mulch.
- Inspect plants and soil in the area to be mulched. Determine whether drainage is adequate. Determine whether there are plants that may be affected by the choice of mulch. Most commonly available mulches work well in most landscapes. Some plants may benefit from the use of a slightly acidifying mulch such as pine bark.
- If mulch is already present, check the depth. Do not add mulch if there is a sufficient layer in place. Rake the old mulch to break up any matted layers and to refresh the appearance. Some landscape maintenance companies spray mulch with a water-soluble, vegetable-based dye to improve the appearance.
- If mulch is piled against the stems or tree trunks, pull it back several inches so that the base of the trunk and the root crown are exposed.
- Organic mulches usually are preferred to inorganic materials due to their soil-enhancing properties. If organic mulch is used, it should be well aerated and, preferably, composted. Avoid sour-smelling mulch.
- Composted wood chips can make good mulch, especially when they contain a blend of leaves, bark, and wood. Fresh wood chips also may be used around established trees and shrubs. Avoid using non-composted wood chips that have been piled deeply without exposure to oxygen.
- For well-drained sites, apply a 2- to 4-inch layer of mulch. If there are drainage problems, a thinner layer should be used. Avoid placing mulch against the tree trunks. Place mulch out to the tree’s drip line or beyond.
Remember: If the tree had a say in the matter, its entire root system (which usually extends well beyond the drip line) would be mulched.
Pruning Your Trees
Pruning Young Trees
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.
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.
For most young trees, maintain a single dominant leader. 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 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 radially, 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.
Newly Planted Trees
Pruning of newly planted trees should be limited to corrective pruning. Remove torn or broken branches, and save other pruning measures for the second or third year.
The belief that trees should be pruned when planted to compensate for root loss is misguided. Trees need their leaves and shoot tips to provide food and the substances that stimulate new root production. Un-pruned trees establish faster with a stronger root system than trees pruned at the time of planting.
Wound dressings were once thought to accelerate wound closure, protect against insects and diseases, and reduce decay.
However, research has shown that dressings do not reduce decay or speed closure and rarely prevent insect or disease infestations. Most experts recommend that wound dressing not be used. If a dressing must be used for cosmetic purposes, use a thin coating of a material that is not toxic to the plant.
Pruning Mature Trees
Pruning is the most common tree maintenance procedure. Although forest trees grow quite well with only nature’s pruning, landscape trees require a higher level of care to maintain their safety and aesthetics. Pruning should be done with an understanding of how the tree responds to each cut. Improper pruning can cause damage that will last for the life of the tree, or worse, shorten the tree’s life.
Reasons for Pruning
Because each cut has the potential to change the growth of the tree, no branch should be removed without a reason. Common reasons for pruning are to remove dead branches, to remove crowded or rubbing limbs, and to eliminate hazards. Trees may also be pruned to increase light and air penetration to the inside of the tree’s crown or to the landscape below. In most cases, mature trees are pruned as a corrective or preventive measure.
Routine thinning does not necessarily improve the health of a tree. Trees produce a dense crown of leaves to manufacture the sugar used as energy for growth and development. Removal of foliage through pruning can reduce growth and stored energy reserves. Heavy pruning can be a significant health stress for the tree.
Yet if people and trees are to coexist in an urban or suburban environment, then we sometimes have to modify the trees. City environments do not mimic natural forest conditions. Safety is a major concern. Also, we want trees to complement other landscape plantings and lawns. Proper pruning, with an understanding of tree biology, can maintain good tree health and structure while enhancing the aesthetic and economic values of our landscapes.
When to Prune
Most routine pruning to remove weak, diseased, or dead limbs can be accomplished at any time during the year with little effect on the tree. As a rule, growth is maximized and wound closure is fastest if pruning takes place before the spring growth flush. Some trees, such as maples and birches, tend to “bleed” if pruned early in the spring. It may be unsightly, but it is of little consequence to the tree.
A few tree diseases, such as oak wilt, can be spread when pruning wounds allow spores access into the tree. Susceptible trees should not be pruned during active transmission periods.
Heavy pruning just after the spring growth flush should be avoided. At that time, trees have just expended a great deal of energy to produce foliage and early shoot growth. Removal of a large percentage of foliage at that time can stress the tree.
Making Proper Pruning Cuts
Pruning cuts should be made just outside the branch collar. The branch collar contains trunk or parent branch tissue and should not be damaged or removed. If the trunk collar has grown out on a dead limb to be removed, make the cut just beyond the collar. Do not cut the collar.
If a large limb is to be removed, its weight should first be reduced. This is done by making an undercut about 12 to 18 inches from the limb’s point of attachment. Make a second cut from the top, directly above or a few inches farther out on the limb. Doing so removes the limb, leaving the 12- to 18-inch stub. Remove the stub by cutting back to the branch collar. This technique reduces the possibility of tearing the bark.
Specific types of pruning may be necessary to maintain a mature tree in a healthy, safe, and attractive condition.
Cleaning is the removal of dead, dying, diseased, crowded, weakly attached and low-vigor branches from the crown of a tree.
Thinning is the selective removal of branches to increase light penetration and air movement through the crown. Thinning opens the foliage of a tree, reduces weight on heavy limbs, and helps retain the tree’s natural shape.
Raising removes the lower branches from a tree in order to provide clearance for buildings, vehicles, pedestrians, and vistas.
Reduction reduces the size of a tree, often for clear- ance for utility lines. Reducing the height or spread of a tree is best accomplished by pruning back the leaders and branch terminals to lateral branches that are large enough to assume the terminal roles (at least one-third the diameter of the cut stem). Compared to topping, reduction helps maintain the form and structural integrity of the tree.
How Much Should Be Pruned?
The amount of live tissue that should be removed depends on the tree size, species, and age, as well as the pruning objectives. Younger trees tolerate the removal of a higher percentage of living tissue better than mature trees do. An important principle to remember is that a tree can recover from several small pruning wounds faster than from one large wound.
A common mistake is to remove too much inner foliage and small branches. It is important to maintain an even distribution of foliage along large limbs and in the lower portion of the crown. Over-thinning reduces the tree’s sugar production capacity and can create tip-heavy limbs that are prone to failure.
Mature trees should require little routine pruning. A widely accepted rule of thumb is never to remove more than one-quarter of a tree’s leaf-bearing crown. In a mature tree, pruning even that much could have negative effects. Removing even a single, large-diameter limb can create a wound that the tree may not be able to close. The older and larger a tree becomes, the less energy it has in reserve to close wounds and defend against decay or insect attack. The pruning of large mature trees is usually limited to removal of dead or potentially hazardous limbs.
Wound dressings were once thought to accelerate wound closure, protect against insects and diseases, and reduce decay. However, research has shown that dressings do not reduce decay or speed closure and rarely prevent insect or disease infestations. Most experts recommend that wound dressings not be used. If a dressing must be used for cosmetic purposes, then only a thin coating of a nontoxic material should be applied.
Hiring an Arborist
Pruning large trees can be dangerous. If pruning involves working above the ground or using power equipment, it is best to hire a professional arborist. An arborist can determine the type of pruning necessary to improve the health, appearance, and safety of your trees. A professional arborist can provide the services of a trained crew, with all of the required safety equipment and liability insurance.
There are a variety of things to look for when selecting an arborist:
- 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)
- Certification through ISA’s Certified Arborist program
- Proof of insurance
- List of references (don’t hesitate to check)
Avoid using the services of any tree company that:
- Advertises topping as a service provided; knowledgeable arborists know that topping is harmful to trees and is not an accepted practice
- Uses tree climbing spikes to climb trees that are being pruned; climbing spikes can damage trees, and their use should be limited to trees that are being removed
Tree Hazards and Treatments
Why Tree Topping Hurts
Topping is perhaps the most harmful tree pruning practice known. Yet, despite more than 25 years of literature and seminars explaining its harmful effects, topping remains a common practice. This brochure explains why topping is not an acceptable pruning technique and offers better alternatives
What is Topping?
Topping is the indiscriminate cutting of tree branches to stubs or lateral branches that are not large enough to assume the terminal role. Other names for topping include “heading,” “tipping,” “hat-racking,” and “rounding over.”
The most common reason given for topping is to reduce the size of a tree. Home owners often feel that their trees have become too large for their property. People fear that tall trees may pose a hazard. Topping, however, is not a viable method of height reduction and certainly does not reduce the hazard. In fact, topping will make a tree more hazardous in the long term.
Topping Causes Decay
The preferred location to make a pruning cut is just beyond the branch collar at the branch’s point of attachment. The tree is biologically equipped to close such a wound, provided the tree is healthy enough and the wound is not too large. Cuts made along a limb between lateral branches create stubs with wounds that the tree may not be able to close. The exposed wood tissues begin to decay. Normally, a tree will “wall off,” or compartmentalize, the decaying tissues, but few trees can defend the multiple severe wounds caused by topping. The decay organisms are given a free path to move down through the branches.
Topping Stresses Trees
Topping often removes 50 to 100 percent of the leaf-bearing crown of a tree. Because leaves are the food factories of a tree, removing them can temporarily starve a tree. The severity of the pruning triggers a sort of survival mechanism. The tree activates latent buds, forcing the rapid growth of multiple shoots below each cut. The tree needs to put out a new crop of leaves as soon as possible. If a tree does not have the stored energy reserves to do so, it will be seriously weakened and may die.
A stressed tree is more vulnerable to insect and disease infestations. Large, open pruning wounds expose the sapwood and heartwood to attacks. The tree may lack sufficient energy to chemically defend the wounds against invasion, and some insects are actually attracted to the chemical signals trees release.
Topping Can Lead to Sunburn
Branches within a tree’s crown produce thousands of leaves to absorb sunlight. When the leaves are removed, the remaining branches and trunk are suddenly exposed to high levels of light and heat. The result may be sunburn of the tissues beneath the bark, which can lead to cankers, bark splitting, and death of some branches.
Topping Creates Hazards
The survival mechanism that causes a tree to produce multiple shoots below each topping cut comes at great expense to the tree. These shoots develop from buds near the surface of the old branches. Unlike normal branches that develop in a socket of overlapping wood tissues, these new shoots are anchored only in the outermost layers of the parent branches.
The new shoots grow quickly, as much as 20 feet in one year, in some species. Unfortunately, the shoots are prone to breaking, especially during windy conditions. The irony is that while the goal was to reduce the tree’s height to make it safer, it has been made more hazardous than before.
Topping Makes Trees Ugly
The natural branching structure of a tree is a biological wonder. Trees form a variety of shapes and growth habits, all with the same goal of presenting their leaves to the sun. Topping removes the ends of the branches, often leaving ugly stubs. Topping destroys the natural form of a tree.
Without leaves (up to 6 months of the year in temperate climates), a topped tree appears disfigured and mutilated. With leaves, it is a dense ball of foliage, lacking its simple grace. A tree that has been topped can never fully regain its natural form.
Topping Is Expensive
The cost of topping a tree is not limited to what the perpetrator is paid. If the tree survives, it will require pruning again within a few years. It will either need to be reduced again or storm damage will have to be cleaned up. If the tree dies, it will have to be removed.
Topping is a high-maintenance pruning practice, with some hidden costs. One is the reduction in property value. Healthy, well-maintained trees can add 10 to 20 percent to the value of a property. Disfigured, topped trees are considered an impending expense.
Another possible cost of topped trees is potential liability. Topped trees are prone to breaking and can be hazardous. Because topping is considered an unacceptable pruning practice, any damage caused by branch failure of a topped tree may lead to a finding of negligence in a court of law.
Alternatives to Topping
Sometimes a tree must be reduced in height or spread. Providing clearance for utility lines is an example. There are recommended techniques for doing so. If practical, branches should be removed back to their point of origin. If a branch must be shortened, it should be cut back to a lateral that is large enough to assume the terminal role. A rule of thumb is to cut back to a lateral that is at least one-third the diameter of the limb being removed.
This method of branch reduction helps to preserve the natural form of the tree. However, if large cuts are involved, the tree may not be able to close over and compartmentalize the wounds. Sometimes the best solution is to remove the tree and replace it with a species that is more appropriate for the site.
Insects and Disease Problems
Insects and diseases can threaten tree health. As soon as you notice any abnormality in your tree’s appearance, you should begin a careful examination of the problem. By identifying the specific symptoms of damage and understanding their causes, you may be able to diagnose the problem and select an appropriate treatment.
Basic elements that influence plant health include sufficient water and light, and a proper balance of nutrients. Too much or too little of any of these environmental conditions may cause plant stress.
Environmental stress weakens plants and makes them more susceptible to insect and disease attack.
Trees deal with environmental stresses, such as shading and competition for water and nutrients in their native environment, by adjusting their growth and development patterns to reflect the availability of the resources. Although trees are adapted to living in stressful conditions in nature, many times the stresses they experience in the landscape are more than they can handle and may make them more susceptible to insects and diseases.
Correct diagnosis of plant health problems requires a careful examination of the situation.
- Accurately identify the plant. Because many insects and diseases are plant-specific, this information can quickly limit the number of suspected diseases and disorders.
- Look for a pattern of abnormality. It may be helpful to compare the affected plant with other plants on the site, especially those of the same species. Differences in color or growth may present clues as to the source of the problem. Non-uniform damage patterns may indicate insects or diseases. Uniform damage over a large area (perhaps several plant species) usually indicates disorders caused by such factors as physical injury, poor drainage, or weather.
- Carefully examine the landscape. The history of the property and adjacent land may reveal many problems. The number of species affected may also help distinguish between infectious pathogens that are more plant-specific as compared to chemical or environmental factors that affect many different species. Most living pathogens take a relatively long time to spread throughout an area, so if a large percentage of plants becomes diseased virtually overnight, a pathogen is probably not involved.
- Examine the roots. Note their color: brown or black roots may signal problems. Brown roots often indicate dry soil conditions or the presence of toxic chemicals. Black roots usually reflect overly wet soil or the presence of root-rotting organisms.
- Check the trunk and branches. Examine the trunk thoroughly for wounds because they provide entrances for pathogens and wood-rotting organisms. Wounds can be caused by weather, fire, lawn mowers, and rodents, as well as a variety of other environmental and mechanical factors. Large defects may indicate a potentially hazardous tree.
Note the position and appearance of affected leaves. Dead leaves at the top of the tree are usually the result of environmental or mechanical root stress. Twisted or curled leaves may indicate viral infection, insect feeding, or exposure to herbicides. The size and color of the foliage may tell a great deal about the plant’s condition. Make note of these and any other abnormalities.
Three things are required for a disease to develop:
- the presence of a pathogen (the disease-causing agent)
- plant susceptibility to that particular pathogen
- an environment suitable for disease development
Plants vary in susceptibility to pathogens. Many disease-prevention programs focus on the use of pathogen-resistant plant varieties. Even if the pathogen is present and a susceptible plant host is available, the proper environmental conditions must be present over the correct period of time for the pathogen to infect the plant.
Diseases can be classified into two broad categories: those caused by infectious or living agents (diseases) and those caused by noninfectious or nonliving agents (disorders).
Examples of infectious agents include fungi, viruses, and bacteria. Noninfectious diseases, which account for 70 to 90 percent of all plant problems in urban areas, can be caused by such factors as nutrient deficiencies, temperature extremes, vandalism, pollutants, and fluctuations in moisture. Noninfectious disorders often produce symptoms similar to those caused by infectious diseases; therefore, it is essential to distinguish between the two in order to give proper treatment.
Some insects can cause injury and damage to trees and shrubs. By defoliating trees or sucking their sap, insects can retard plant growth. By boring into the trunk and branches, they interfere with sap flow and weaken the tree structure. Insects may also carry some plant diseases. In many cases, however, the insect problem is secondary to problems brought on by a stress disorder or pathogen.
It is important to remember that most insects are beneficial rather than destructive. They help with pollination or act as predators of more harmful species. Therefore, killing all insects without regard to their kind and function can actually be detrimental to tree health.
Insects may be divided into three categories according to their method of feeding: chewing, sucking, or boring. Insects from each group have characteristic patterns of damage that will help you determine the culprit and the proper treatment. Always consult a tree care expert if you have any doubt about the nature of the insect problem or the proper treatment
Chewing insects eat plant tissue such as leaves, flowers, buds, and twigs. Indications of damage by these insects are often seen by uneven or broken margins on the leaves, skeletonization of the leaves, and leaf mining. Chewing insects can be beetle adults or larvae, moth larvae (caterpillars), and many other groups of insects. The damage they cause (leaf notching, leaf mining, leaf skeletonizing, etc.) will help in identifying the pest insect.
Sucking insects insert their beak (proboscis) into the tissues of leaves, twigs, branches, flowers, or fruit and then feed on the plant’s juices. Some examples of sucking insects are aphids, mealy bugs, thrips, and leafhoppers. Damage caused by these pests is often indicated by discoloration, drooping, wilting, leaf spots (stippling), honeydew, or general lack of vigor in the affected plant.
Boring insects spend time feeding somewhere beneath the bark of a tree as larvae. Some borers kill twigs and leaders when adults feed or when eggs hatch into larvae that bore into the stem and develop into adults. Other borers, known as bark beetles, mate at or near the bark surface, and adults lay eggs in tunnels beneath the bark.
The treatment method used for a particular insect or disease problem will depend on the species involved, the extent of the problem, and a variety of other factors specific to the situation and local regulations. Always consult a professional if you have any doubt about the nature of the problem or proper treatment.
Recognizing Tree Hazards
Trees provide significant benefits to our homes and cities, but when trees fall and injure people or damage property, they are liabilities. Taking care of tree hazards makes your property safer and prolongs the life of the tree.
Trees are an important part of our world. They offer a wide range of benefits to the environment and provide tremendous beauty.
However, trees may be dangerous. Trees or parts of trees may fall and cause injury to people or damage to property. We call trees in such situations hazardous, to signify the risk involved with their presence. While every tree has the potential to fall, only a small number actually hit something or someone.
It is an owner’s responsibility to provide for the safety of trees on his or her property. This brochure provides some tips for identifying the common defects associated with tree hazards. However, evaluating the seriousness of these defects is best done by a professional arborist. Regular tree care will help identify hazardous trees and the risk they present. Once the hazard is recognized, steps may be taken to reduce the likelihood of the tree falling and injuring someone.
Hazardous Trees and Utility Lines
Trees that fall into utility lines have additional serious consequences. Not only can they injure people or property near the line, but hitting a line may cause power outages, surges, fires, and other damage. Downed lines still conducting electricity are especially dangerous. A tree with a potential to fall into a utility line is a very serious situation.
Tree Hazard Checklist
Consider these questions:
- Are there large dead branches in the tree?
- Are there detached branches hanging in the tree?
- Does the tree have cavities or rotten wood along the trunk or in major branches?
- Are mushrooms present at the base of the tree?
- Are there cracks or splits in the trunk or where branches are attached?
- Have any branches fallen from the tree?
- Have adjacent trees fallen over or died?
- Has the trunk developed a strong lean?
- Do many of the major branches arise from one point on the trunk?
- Have the roots been broken off, injured, or damaged by lowering the soil level, installing pavement, repairing sidewalks, or digging trenches?
- Has the site recently been changed by construction, raising the soil level, or installing lawns?
- Have the leaves prematurely developed an unusual color or size?
- Have trees in adjacent wooded areas been removed?
- Has the tree been topped or otherwise heavily pruned?
Defects in Urban Trees
The following are defects or signs of possible defects in urban trees (see figure):
- re-growth from topping, line clearance, or other pruning
- electrical line adjacent to tree
- broken or partially attached branch
- open cavity in trunk or branch
- dead or dying branches
- branches arising from a single point on the trunk
- decay and rot present in old wounds
- recent change in grade or soil level, or other construction
Defects in Rural Trees
The following are defects or signs of possible defects in rural trees (see figure):
- recent site construction, grading and tree removal, clearing of forests for development
- previous tree failures in the local area
- tree leaning near a target
- forked trunk; branches and stems equal in size
- wet areas with shallow soil
Managing Tree Hazards
An arborist can help you manage the trees on your property and can provide treatments that may help make your tree safer, reducing the risk associated with hazardous trees. An arborist familiar with hazard tree evaluation may suggest one or more of the following:
- Remove the target. While a home or a nearby power line cannot be moved, it is possible to move picnic tables, cars, landscape features, or other possible targets to prevent them from being hit by a falling tree.
- Prune the tree. Remove the defective branches of the tree. Because inappropriate pruning may weaken a tree, pruning work is best done by an ISA Certified Arborist.
- Cable and brace the tree. Provide physical support for weak branches and stems to increase their strength and stability.
- Provide routine care. Mature trees need routine care in the form of water, fertilizer (in some cases), mulch, and pruning as dictated by the season and their structure.
- Remove the tree. Some hazardous trees are best removed. If possible, plant a new tree in an appropriate place as a replacement.
Recognizing and reducing tree hazards not only increases the safety of your property and that of your neighbors but also improve the tree’s health and may increase its longevity!
Ensuring Quality Care for Your Tree
Trees are assets to your home and community and deserve the best possible care. If you answered “yes” to any of the questions in the tree hazard checklist or see any of the defects contained in the illustrations, your tree should be examined by an ISA Certified Arborist.
Avoiding Tree Damage During Construction
As cities and suburbs expand, wooded lands are being developed into commercial and residential sites. Homes are constructed in the midst of trees to take advantage of the aesthetic and environmental value of the wooded lots. Wooded properties can be worth as much as 20 percent more than those without trees, and people value the opportunity to live among trees.
Unfortunately, the processes involved with construction can be deadly to nearby trees. Unless the damage is extreme, the trees may not die immediately but could decline over several years. With this delay in symptom development, you may not associate the loss of the tree with the construction.
It is possible to preserve trees on building sites if the right measures are taken. The most important step is to hire a professional arborist during the planning stage. An arborist can help you decide which trees can be saved and can work with the builder to protect the trees throughout each construction phase.
How Trees Are Damaged During Construction
Physical Injury to Trunk and Crown. Construction equipment can injure the aboveground portion of a tree by breaking branches, tearing the bark, and wounding the trunk. These injuries are permanent and, if extensive, can be fatal.
Cutting of Roots. The digging and trenching that are necessary to construct a house and install underground utilities will likely sever a portion of the roots of many trees in the area. It is easy to appreciate the potential for damage if you understand where roots grow. The roots of a tree are found mostly in the upper 6 to 12 inches of the soil. In a mature tree, the roots extend far from the trunk. In fact, roots typically are found growing a distance of one to three times the height of the tree. The amount of damage a tree can suffer from root loss depends, in part, on how close to the tree the cut is made. Severing one major root can cause the loss of 5 to 20 percent of the root system.
Another problem that may result from root loss caused by digging and trenching is that the potential for the trees to fall over is increased. The roots play a critical role in anchoring a tree. If the major support roots are cut on one side of a tree, the tree may fall or blow over.
Less damage is done to tree roots if utilities are tunneled under a tree rather than across the roots.
Soil Compaction. An ideal soil for root growth and development is about 50 percent pore space. These pores—the spaces between soil particles—are filled with water and air. The heavy equipment used in construction com-pacts the soil and can dramatically reduce the amount of pore space. This compaction not only inhibits root growth and penetration but also decreases oxygen in the soil that is essential to the growth and function of the roots.
Smothering Roots by Adding Soil. Most people are surprised to learn that 90 percent of the fine roots that absorb water and minerals are in the upper 6 to 12 inches of soil. Roots require space, air, and water. Roots grow best where these requirements are met, which is usually near the soil surface. Piling soil over the root system or increasing the grade smothers the roots. It takes only a few inches of added soil to kill a sensitive mature tree.
Exposure to the Elements. Trees in a forest grow as a community, protecting each other from the elements. The trees grow tall, with long, straight trunks and high canopies. Removing neighboring trees or opening the shared canopies of trees during construction exposes the remaining trees to sunlight and wind. The higher levels of sunlight may cause sunscald on the trunks and branches. Also, the remaining trees are more prone to breaking from wind or ice loading.
Hire a professional arborist in the early planning stage. Many of the trees on your property may be saved if the proper steps are taken. Allow the arborist to meet with you and your building contractor. Your arborist can assess the trees on your property, determine which are healthy and structurally sound, and suggest measures to preserve and protect them.
One of the first decisions is determining which trees are to be preserved and which should be removed. You must consider the species, size, maturity, location, and condition of each tree. The largest, most mature trees are not always the best choices to preserve. Younger, more vigorous trees usually can survive and adapt to the stresses of construction better. Try to maintain diversity of species and ages. Your arborist can advise you about which trees are more sensitive to compaction, grade changes, and root damage.
Your arborist and builder should work together in planning the construction. The builder may need to be educated regarding the value of the trees on your property and the importance of saving them. Few builders are aware of the way trees’ roots grow and what must be done to protect them.
Sometimes small changes in the placement or design of your house can make a great difference in whether a critical tree will survive. An alternative plan may be friendlier to the root system.
For example, bridging over the roots may substitute for a conventional walkway. Because trenching near a tree for utility installation can be damaging, tunneling under the root system may be a good option.
Because our ability to repair construction damage to trees is limited, it is vital that trees be protected from injury. The single most important action you can take is to set up construction fences around all of the trees that are to remain. The fences should be placed as far out from the trunks of the trees as possible. As a general guideline, allow 1 foot of space from the trunk for each inch of trunk diameter. The intent is not merely to protect the aboveground portions of the trees but also the root systems. Remember that the root systems extend much farther than the drip lines of the trees.
Instruct construction personnel to keep the fenced area clear of building materials, waste, and excess soil. No digging, trenching, or other soil disturbance should be allowed in the fenced area.
Protective fences should be erected as far out from the trunks as possible in order to protect the root system.
If at all possible, it is best to allow only one access route on and off the property. All contractors must be instructed where they are permitted to drive and park their vehicles. Often this same access drive can later serve as the route for utility wires, water lines, or the driveway.
Specify storage areas for equipment, soil, and construction materials. Limit areas for burning (if permitted), cement wash-out pits, and construction work zones. These areas should be away from protected trees.
Get it in writing. All of the measures intended to protect your trees must be written into the construction specifications. The written specifications should detail exactly what can and cannot be done to and around the trees. Each subcontractor must be made aware of the barriers, limitations, and specified work zones. It is a good idea to post signs as a reminder.
Fines and penalties for violations should be built into the specifications. Not too surprisingly, subcontractors are much more likely to adhere to the tree preservation clauses if their profit is at stake. The severity of the fines should be proportional to the potential damage to the trees and should increase for multiple infractions.
Maintaining Good Communications
It is important to work together as a team. You may share clear objectives with your arborist and your builder, but one subcontractor can destroy your prudent efforts. Construction damage to trees is often irreversible.
Visit the site at least once a day if possible. Your vigilance will pay off as workers learn to take your wishes seriously. Take photos at every stage of construction. If any infraction of the specifications does occur, it will be important to prove liability.
It is not unusual to go to great lengths to preserve trees during construction, only to have them injured during landscaping. Installing irrigation systems and rototilling planting beds are two ways the root systems of trees can be damaged. Remember also that small increases in grade (as little as 2 to 6 inches) that place additional soil over the roots can be devastating to your trees. Careful planning and communicating with landscape designers and contractors is just as important as avoiding tree damage during construction.
Post-Construction Tree Maintenance
Your trees will require several years to adjust to the injury and environmental changes that occur during construction. Stressed trees are more prone to health problems such as disease and insect infestations. Talk to your arborist about continued maintenance for your trees. Continue to monitor your trees, and have them periodically evaluated for declining health or safety hazards.
Despite the best intentions and most stringent tree preservation measures, your trees still might be injured from the construction process. Your arborist can suggest remedial treatments to help reduce stress and improve the growing conditions around your trees
Treatment of Trees Damaged by Construction
The processes involved with construction can be devastating to the surrounding trees if no measures have been taken to protect them. The visible injuries such as broken branches and wounds to tree trunks are only the beginning. It is the damage to the root systems that often result in tree loss.
In an ideal situation, an arborist is called in to consult in the planning stages of construction. Trees can be preserved if the appropriate measures are taken soon enough. Unfortunately, it is usually when the first signs of decline appear that help is sought.
There are some remedial treatments that may save some construction-damaged trees, but immediate implementation is critical. If you have trees that have been affected by recent construction, consult a professional arborist promptly. Your arborist can assess each tree for viability and potential hazards, and recommend treatments.
Damage Caused By Construction
- physical injury to the trunk and crown
- soil compaction in the root zone
- severing of roots
- smothering roots by adding soil
- split and broken branches
- new exposure to wind and sunlight
Inspection and Assessment
Because construction damage can affect the structure and stability of a tree, your arborist should check for potential hazards. A hazard check may involve a simple visual inspection, or instruments may be used to check for the presence of decay. If a hazard is found, sometimes it can be reduced or eliminated by removing an unsafe limb, pruning to reduce weight, or installing cables or braces to provide structural support. An often overlooked method of reducing hazards is to move objects that could be hit or to limit access to the hazardous area. If there is doubt about the structural integrity of a tree or the hazard cannot be adequately reduced, it should be removed. Although the goal is to preserve trees whenever possible, that goal must not supersede any question of safety.
Treating Trunk and Crown Injuries
Pruning. Branches that are split, torn, or broken should be removed. Also, remove any dead, diseased, or rubbing limbs from the crown of the tree. Sometimes it is necessary to remove some lower limbs to raise the canopy of a tree and provide clearance below. It is best to postpone other maintenance pruning for a few years. It used to be recommended that tree canopies be thinned or topped to compensate for root loss. There is no conclusive research to support this practice. Thinning the crown can reduce a tree’s food-making capability and may stress the tree further. It is better to limit pruning in the first few years to hazard reduction and the removal of deadwood. Do not top the trees.
Cabling and Bracing. Trees growing in wooded areas are usually not a threat to people or structures. Trees that are close to houses or other buildings must be maintained to keep them structurally sound. If branches or tree trunks need additional support, a professional arborist may be able to install cables or bracing rods. If cables or braces are installed, they must be inspected regularly. The amount of added security offered by the installation of support hardware is limited. Not all weak limbs are candidates for these measures.
Repairing Damaged Bark and Trunk Wounds. Often the bark may be damaged along the trunk or major limbs. If that happens, remove the loose bark. Jagged edges can be cut away with a sharp knife. Take care not to cut into living tissues.
Wound dressings were once thought to accelerate wound closure, protect against insects and diseases, and reduce decay. However, research has shown that dressings generally do not reduce decay or speed closure and rarely prevent insect or disease infestations. Most experts recommend that wound dressings not be used. If a dressing must be used for cosmetic purposes, use just a thin coating of a nontoxic material.
Irrigation and Drainage
One of the most important tree maintenance procedures following construction damage is to maintain an adequate, but not excessive, supply of water to the root zone. If there is a drainage problem, the trees will decline rapidly. Improper drainage must be corrected if the trees are to be saved. If soil drainage is good, be sure to keep the trees well watered, especially during the dry summer months. A long, slow soak over the entire root zone is the preferred method of watering. Keep the top 12 inches moist, but avoid over-watering. Avoid frequent, shallow watering. Make sure surface water drains away from the tree. Proper irrigation may do more to help trees recover from construction stress than anything else you could do.
One of the simplest and least expensive things you can do for your trees may also be one of the most effective. Applying a 2- to 4-inch layer of organic mulch such as wood chips, shredded bark, or pine needles over the root system of a tree can enhance root growth. The mulch helps condition the soil, moderates soil temperatures, maintains moisture, and reduces competition from weeds and grass. The mulch should extend as far out from the tree as practical for the landscape site. (If the tree had a say, its entire root system would be mulched.) Do not apply the mulch any deeper than 4 inches, and do not pile it against the trunk.
Improving Aeration of the Root Zone
Drilling Holes/Vertical Mulching
Compactions of the soil and increases in grade both have the effect of depleting the oxygen supply to tree roots. If soil aeration can be improved, root growth and water uptake can be enhanced.
A common method of aeration of the root zone involves drilling holes in the ground. Holes are usually 2 to 4 inches in diameter and are made about 3 feet on center throughout the root zone of the tree. The depth should be at least 12 inches but may need to be deeper if the soil grade has been raised. Sometimes the holes are filled with peat moss, wood chips, pea gravel, or other materials that maintain aeration and support root growth. This process is called vertical mulching.
More recent research has shown promising results with another method of aeration called radial aeration. Narrow trenches are cut with a compressed air gun in a radial pattern throughout the root zone. These trenches appear similar to the spokes of a wagon wheel. It is important to begin the trenches 4 to 8 feet from the trunk of the tree to avoid cutting any major support roots. The trenches should extend at least as far as the drip line of the tree. If the primary goal is to reduce compaction, the trenches should be about 8 to 12 inches in depth. They may need to be deeper if the soil grade has been raised.
The narrow trenches can be backfilled with topsoil or compost. Root growth will be greater in the trenched area than in the surrounding soil. This treatment can give a tree the added boost it needs to adapt to the compacted soil or new grade.
Vertical mulching and radial trenching are techniques that may improve conditions for root growth. If construction-damaged trees are to survive the injuries and stresses they have suffered, they must replace the roots that have been lost.
What About Fertilization?
Most experts recommend that you do not fertilize your trees the first year after construction damage. Water and mineral uptake may be reduced because of root damage. Excessive soil salts can draw water out of the roots and into the soil. In addition, nitrogen fertilization may stimulate top growth at the expense of root growth. It is a common misconception that applying fertilizer gives a stressed tree a much-needed shot in the arm. Fertilization should be based on the nutritional needs of trees on a site. Soils can be analyzed to determine whether any of the essential minerals are deficient. If soil nutrients are deficient, supplemental fertilization may be indicated. It is advisable to keep application rates low until the root system has had time to adjust.
Monitoring for Decline and Hazards
Despite your best efforts, you may lose some trees from the construction damage. Symptoms of decline include smaller and fewer leaves, dieback in the crown of the tree, and premature fall color. If a tree dies as a result of root damage, it may be an immediate hazard and should be removed right away. Examine your trees for signs of possible hazards. Look for cracks in the trunk, split or broken branches, and dead limbs. Watch for indications of internal decay such as cavities, carpenter ants, soft wood, and mushroom-like structures growing on the trunk, root crown, or along the major roots. If you detect any defects or suspect decay, consult an arborist for a professional assessment. It is prudent to have your trees evaluated periodically by a professional. You should also inspect your trees for signs of insects or diseases. Stressed trees are more prone to attack by certain pests. Talk to your arborist about putting your trees on a program of Plant Health Care (PHC). Such a program may help identify and treat problems before they become a threat to the life of your trees.