An arborist, by definition, is an individual trained in the art and science of selecting, planting, and maintaining individual trees. Arborists are knowledgeable about the needs of trees and are trained and equipped to safely provide proper tree care.
Well-cared-for trees are attractive and can add property value. A study conducted in Cincinnati neighborhoods demonstrated that the average value of tree canopy was 10.7% of the sale price of homes (Dimke et al., 2013).
Communities also benefit. Urban trees filter airborne particulates, release oxygen, absorb carbon dioxide, and intercept stormwater runoff. Their shade can reduce energy use by lowering air conditioning needs and their wind blockage can reduce heating demands (Wolf, et al., 2020).
Studies show that healthy urban trees have positive effects on human health (Jonnes 2011; Nowak et al. 2014). Indeed, the title of an article on the impacts of the non-native ash tree-killer, emerald ash borer (Agrilus planipennis Fairmaire), “When Trees Die, People Die,” says it all (Abrams 2013).
Conversely, poorly maintained trees can reduce property values and become a significant liability, threatening structures and even human life as illustrated in Figure 2. Mismanaged pest and disease problems can significantly shorten tree lifespans. Pruning or removing trees, especially large trees, can be dangerous work. Such tree work should only be done by a tree-care professional trained and equipped to work safely in and around trees.
The Different Types of Arborists
The International Society of Arboriculture (ISA) is a non-profit organization for tree-care professionals that provides proof of expertise through credentials. Tree-care professionals earn ISA credentials through testing, and they maintain their credentials through continuing education. Seeking an ISA-credentialed arborist is the first step in getting expert help from a tree-care professional.
Figure 4 shows the different types of ISA credentials. Tree-care workers cannot attain any other ISA credential without first earning the ISA Certified Arborist credential. Certified Arborists are trained in tree biology; soil management and fertilization; tree installation and establishment; pruning; tree diagnostics and treatment; protecting trees from construction damage; and tree worker safety.
Two credentials fall under the heading of ISA Certified Tree Workers. An ISA Climber Specialist is skilled at climbing trees and as an ISA Certified Arborist, Certified Tree Workers are able to evaluate trees high in a tree’s canopy. This is important for diagnosing certain pest and disease issues, particularly stem decay.
They are also experts at determining where to make pruning cuts and safely pruning large trees without causing property damage. Equally important, as shown in Figure 5, Climber Specialists are skilled in safely taking down large trees that pose a serious risk to lives and property if taken down by non-professionals.
If you are hiring a tree-care company to perform branch removal on a large, mature tree, and the work involves climbing the tree, it’s important to ask for an ISA Climber Specialist to do the work.
An ISA Aerial Lift Specialist does the same kind of tree evaluations, pruning, and tree removal work as a climber. However, as shown in Figures 6 and 7, Lift Specialists perform their work using an aerial lift. Again, safety is the primary concern for your property and the arborist. You should not allow a tree worker to use an aerial lift on your property unless they are an ISA Aerial Lift Specialist.
ISA Climber and Lift Specialists are trained to safely work around electrical utility lines. However, an ISA Utility Specialist has specific training on how to safely perform tree work around all electrical lines including high voltage lines. Thus, these specialists are mostly employed by utility and contracting companies for line-clearance work. Their specialty is seldom required for home landscapes.
ISA Municipal Specialists apply their ISA certification training to managing urban trees. You should urge that your community hire a municipal specialist if they are having trees evaluated for any purpose or having work done, such as selective pruning or removing trees.
Finally, an ISA Board Certified Master Arborist (BCMA) has proven expertise across many levels of ISA credentials. They specialize in tree appraisals, diagnosing problems, and recommending tree management options. It is common for BCMAs working for a tree-care company to make the first visit, then provide options offered by the company. They provide an added level of expertise above that which is offered by an ISA Certified Arborist. BCMAs commonly work as consulting arborists with an added level of professionalism demonstrated by membership in the American Society of Consulting Arborists (ASCA).
ISA Tree Risk Assessment Qualification (TRAQ)
Hiring someone to assess whether or not a tree presents a risk to human life and property is a decision that should not be taken lightly. Figures 8 and 9 shows how getting it wrong can have catastrophic consequences leading to the death or injury of property owners as well as arborists. It is a job that should only be done by a tree-care professional who has earned the ISA TRAQ credential.
TRAQ-credentialed professionals have proven expertise across many arboricultural disciplines from tree biomechanics to soil structural characteristics. The TRAQ qualification promotes safety by using a systematic, standardized, tree-risk-assessment process. Tree owners are provided with information that supports decisions to reduce hazardous situations. If trees are found to present a low risk, information is provided on ways to enhance tree health and longevity.
Tips on Selecting an Arborist
To Do:
Double-check who has responsibility for the tree. Trees planted between sidewalks and streets may be in the public right of way which is managed by a local municipal authority. Consult with the municipality’s public works or urban forestry department for clarification.- Decide the type of tree service(s) you need. This will help you to decide what kind of arborist(s) you need.
- Visit the ISA website (isa-arbor.com) and click “Find an Arborist.” You can search for arborists using your zip code or city. You can then see the credentials earned by the arborists in your area.
- Check online, searching under “arborist” or “tree service.” Look for accreditation with the ISA or ASCA.
Clearly describe the type of tree service(s) you need when you contact a tree care company. - Ask for the qualifications of their arborists.
- Obtain several quotes before purchasing tree services. You may have to pay for the estimates, and it will take more time, but it will be worth the investment in the long term.
- Once you have had a positive experience with an arborist, work together in the future to develop a relationship beneficial for the long-term care of your trees.
- Insect pest identification is straightforward because you and the arborist can see the pest. However, if a disease is suspected, check to see how the arborist is confirming the disease. For example, the company should provide proof from a non-biased clinic (i.e., The Ohio State University C. Wayne Ellett Plant and Pest Diagnostic Clinic) that the disease presents a clear and present danger to your tree before you agree to treatments.
- 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 in the community.
- If a pesticide application is being made, the company is required to have a current pesticide applicator license through the Ohio Department of Agriculture.
- Companies should be bonded and insured. You should request certificates of insurance, including proof of liability for personal and property damage (such as your house and your neighbor’s house) and worker's compensation. Phone the insurance company to verify current policy information.
- Request local references for jobs the company or individual has done.
- If possible, talk with the former clients.
NOT to Do’s:
- Beware of door-knocking salespeople who are especially common after storms or when invasive tree species enter the area. When these types of events happen, nonprofessionals see a chance to earn some quick money. Shoddy work can present risks to people and property.
- Never be rushed by bargains or time sensitive deals.
- Don’t always accept the lowest bid. Remember, you get what you pay for.
- Never pay in advance.
Additional Tips:
- A conscientious arborist will not use climbing spikes if the tree is to remain in the landscape. Spikes can damage trees and provide a potential opening for diseases and insects to enter the tree.
- An ISA-credentialed arborist would never recommend “tree topping”(removing the tops of trees as shown in Figure 11). As shown in Figure 12, tree topping encourages the growth of multiple weakly-attached lateral branches prone to breakage. Tree topping is sometimes performed to reduce the risk of branch breakage and tree failure. The practice actually increases such risks (Kuhns & Reiter, 2009).
Figure 13 is a close up of the tree in Figure 12. Note that the main stem is rotting as a result of tree topping. Topped trees are not able to close the large, horizontal wounds, and this leaves the wood (xylem) open to interior decay that descends downward in the trunk. The interior rot decreases the xylem’s structural integrity which increases the risk of trunk breakage and the death of the tree (Karlovch et al., 2000).
- Of course, removing the tops of tree may be required to conform to utility line clearance standards as illustrated in Figure 14. Utility companies are required to keep vegetation away from power and communication lines. Utility companies should not be blamed if tree topping is necessary to maintain customer service. The fault rests with the decision to select and plant trees that can eventually grow into overhead utility lines.
Remember when evaluating bids that reputable arborists have made large investments in equipment and training. Trucks, hydraulic booms, chippers, sprayers, stump cutters, and chain saws represent major capital investments and maintenance costs. Labor, insurance, safety training, and continuing education add to the overhead.
The price for a job reflects all of these costs as well as a margin for profit. Work is usually priced one of two ways:
- A single price for the job.
- An hourly rate plus materials.
The arborist's skill and professionalism may be more important than a low bid to ensure the continued health of your trees.
Most reputable arborists have their clients sign a contract. Be sure to read the contract carefully. Ask questions, such as:
- When will the work be started and completed?
- Who will be responsible for clean-up?
- Does this include stump removal?
- Is this the total price?
- What are the terms of payment?
- If I would like more done, what is your hourly rate?
Ways to Save Money
- Schedule work well in advance. Allowing the company to plan for your work may provide an opportunity to save on costs.
- Talk with neighbors about tree maintenance needs on their properties. An arborist may be interested in a group job over smaller individual jobs.
- Be aware that it is usually less expensive to remove live trees compared to dead trees. Brittle trunks and limbs on dead trees present serious risks to arborists and property which requires additional steps to ensure safety. Thus, if a live tree is found to have life-ending problems, it is best to have the tree removed while it is still alive.
“Never say there is nothing beautiful in the world anymore. There is always something to make you wonder in the shape of a tree, the trembling of a leaf.” - Albert Schweitzer
References
Abrams, L. (2013). When Trees Die, People Die. The Atlantic, 22.
theatlantic.com/health/archive/2013/01/when-trees-die-people-die/267322
Dimke, K. C., Sydnor, T. D., & Gardner, D. S. (2013). The effect of landscape trees on residential property values of six communities in Cincinnati, Ohio. Arboriculture & Urban Forestry (AUF), 39(2), 49–55.
doi.org/10.48044/jauf.2013.007
Jonnes, J. (2011). What Is a Tree Worth? The Wilson Quarterly (1976-), 35(1), 34–41.
jstor.org/stable/41001066
Karlovch, D., Groninger, J. W., & Close, D. D. (2000). Tree condition associated with topping in southern Illinois communities. Journal of Arboriculture, 26(2), 87–91.
DOI:10.48044/jauf.2000.010
Kuhns, M. R., & Reiter, D. K. (2009). Tree care and topping beliefs, knowledge, and practices in six western U.S. cities. Arboriculture & Urban Forestry, 35(3), 122.
auf.isa-arbor.com/content/isa/35/3/122.full.pdf
Nowak, D. J., Hirabayashi, S., Bodine, A., & Greenfield, E. (2014). Tree and forest effects on air quality and human health in the United States. Environmental Pollution, 193, 119–129.
doi.org/10.1016/j.envpol.2014.05.028
Wolf, K. L., Lam, S. T., McKeen, J. K., Richardson, G. R. A., van Den Bosch, M., & Bardekjian, A. C. (2020). Urban trees and human health: A scoping review. International Journal of Environmental Research and Public Health, 17(12), 4371.
doi.org/10.3390/ijerph17124371
Originally written in 1996 by Susan R. Metzger, The Ohio State University.
Rewritten on March 27, 2019, by Amy K. Stone, Extension Educator, Agriculture and Natural Resources, Lucas County; and Cynthia M. Meyer, then Extension Educator, Agriculture and Natural Resources, Butler County, now Conservation Program Specialist, Warren County Soil and Water Conservation District.