How to Hire a Tree Expert

Arborists are tree care professionals trained to properly maintain individual trees throughout their life. Trees can add aesthetic and economic value to a property, and provide energy savings for cooling and heating. Owners are responsible for the care of trees on their property, which is an incentive to maintain healthy, aesthetic, and well cared for trees. Neglected trees can become a liability and potential hazard for people and property. Working in large trees can be dangerous and should only be done by trained professionals with the appropriate equipment. Trees are long-lived organisms that require care appropriate for the species, climate and the location.

Pruning

Arborists inspect trees to determine the type of pruning necessary to maintain or improve the size and health of trees, or minimize risk factors. Common pruning techniques include:

•  Removal of dead, diseased, and insect infested branches.
• Removal of branches that are rubbing and crossing, or storm-damaged.
• Removal of branches that obstruct access to streets, buildings, interfere with utilities, and limit views.
• Removal of branches that improve the tree structure, and lower the risk for storm damage.

Tree removal

Trees live for various amounts of time and when they are at the end of their life or due to external circumstances, they have to be removed. Arborists can recommend the pros and cons of keeping or removing a tree. Reasons for tree removal include: 

• Dead or dying
• Posing an unacceptable risk
• Causing an obstruction that is impossible to correct through pruning
• Interfering with other, more desirable trees
• Undesirable species will be replaced with a better-suited specimen
• Transplanting is not an option

Emergency tree care

Sudden failure of trees due to storms or other accidents can result in trees falling on other trees, streets, cars, or buildings. Removal of fallen trees, often in unstable conditions, requires trained tree care professionals to safely remove especially large trees and prevent further damage.

Planting

Arborist may plant or transplant trees. They may recommend species that are appropriate for a location based on climate, soil, and space. Planting the right tree in the right place prevents future problems due to insufficient growing space, poor adaptation to a site, and potential insect and disease problems.

Other tree services 

Many arborists also provide other tree care services including:

• Preventative maintenance to keep trees healthy
• Fertilization to meet the nutritional needs of trees
• Cabling or bracing for added support to branches with weak attachment
• Soil aeration to improve root growth
• Installing lightning protection systems
• Diagnosing and managing insects and diseases with appropriate methods
• Consulting and legal expert services related to trees

When hiring an arborist, look for certifications, licenses, education, experience, and references.

Reputable Firm 

Beware of people soliciting work door to door without identification on their vehicle, uniform, or I.D. card. This type of solicitations is especially common after storms when there is an opportunity for ‘quick money’. Often storm damage creates high-risk situations for both workers and homeowners, with the potential for even more damage to trees and other plants if the work is not done correctly.  Members of professional organizations such as the International Society of Arboriculture (ISA) or the American Society of Consulting Arborists (ASCA) demonstrate a level of professionalism and interest to stay well informed of the latest techniques and information. ISA certified arborists are trained in tree care and have passed exams to demonstrate professional qualifications that documents their base of knowledge. Certification does not guarantee high quality work, but it does demonstrate a basic level of professional capability and commitment to the field. You can check whether an arborist is certified with ISA by visiting the organization’s website (https://www.isa-arbor.com/) and requesting a list of all certified arborists in your area.

Insurance 

Request proof of insurance from the arborist and confirm with the insurance company (free for both parties) that insurance is still current. Under some circumstances, you can be held financially responsible if an uninsured worker is hurt on your property or damage is done to a neighbor’s property. A reputable arborist carries personal and property damage insurance as well as worker’s compensation. You can find out from the Industrial Commission of Arizona (https://www.azica.gov/) whether the firm carries Workers’ Compensation. Beyond insurance, the Arizona Department of Revenue can confirm that a company is legal and is paying proper taxes.

Reference

Ask for and verify local references. Visit and inspect some of their work, especially work that is similar to what you are requesting. Talk to previous clients. Experience, education and a good reputation are signs of a good arborist.

Have more than one arborist or company give you an estimate. You may be required to pay for the estimate, but two or more opinions are worth the investment, especially for large jobs. The arborist’s skill and professionalism may be more important than a low bid.

While some arborists are not equipped to service every aspect of every job, a good arborist can advise and direct in all areas of tree care (pruning, cabling/bracing, fertilizing, lightning protection, pest control, etc.). Good arborists will only perform industry-accepted practices. If reducing the height of a tree is the goal, a good arborist will use ‘drop crotching’ or ‘crown reduction’ techniques. They will not simply chop off the top of the tree, known as ‘topping’ at the desired height. A good arborist will not use climbing spikes, except in emergencies, if the tree is to remain in the landscape. Beware of an arborist who is eager to remove a living tree. Removal should be the last resort.

Well-cared for trees can increase your property value by up to 5%, in special cases more. Proper care of trees is a good investment and in addition to potentially higher property value, provides other benefits. Commercial arborists have large investments in equipment and training. Trucks, hydraulic booms, chippers, sprayers, stump grinders, and chain saws represent major capital investments and maintenance costs. Labor, insurance, safety training, and continuing education add to the overhead. The price charged for a job reflects all of these costs as well as a reasonable margin of profit. You may cut down on the cost by scheduling your work well in advance. By coordinating with your neighbors, you may be able to obtain a group discount.

A contract is the key to preventing misunderstandings and assuring the work is performed to the standards you expect. Most companies have their own forms, and conditions vary widely. Read the document carefully and check with your attorney if you have questions. A contract should include several key items:

1. The date that work is to begin and end.
2. Exactly what work will be done? For example, ‘Prune all dead, dying, diseased, and weak branches 1.5 inches or greater in diameter.’
3. Specify that the work will be done according to the current American National Standard Institute (ANSI) Tree Care Standards, especially Pruning (ANSI A 300 Part 1) and Safety (Z133) which are adopted as industry standard practices by ISA.
4. If your tree is to be sprayed, get a written statement detailing the specific insect or disease to be treated, the chemical to be used, and how much, and what you need to do (cover outdoor furniture, keep pets inside, etc.).  
5. If fertilizing is to be done, specify type, amount and method of application. A rough map of the property identifying trees to be serviced, or a clearly written description of the location.  
6. Specify what clean-up work will be done and when.
7. Clarify who will get any firewood, and if it is for you, will it be cut into 16-inch lengths and stacked in a certain location?
8. Clarify if the removal of a tree includes grinding out the stump and surface roots to one foot below grade, filling with topsoil, and planting other plants.
9. What is the absolute total dollar amount you will be charged? Leave no room for confusion over whether the price is per tree or for the whole job. Work is usually priced as a single fee for the whole job or on an hourly basis plus materials. When using the latter, be sure to include the wording ‘but not to exceed…’.

Certified arborist  

Certification from the International Society of Arboriculture (ISA). Requires training and knowledge in all aspects of arboriculture and adherence to the code of ethics. To become eligible to take the certification exam, candidates must have up to three years of practical arboricultural experience or a college or university degree. Continuing education units are required to maintain the certification.

Certified tree worker

Certification from the International Society of Arboriculture (ISA). The exam includes a classroom test and a test in the field on all aspects of tree care and a practical exam covering climbing skills and aerial rescue procedures. Requires 18 months of climbing experience in arboriculture and continuing education to maintain the certification.

Consulting arborist    

Anyone may call themselves a consulting arborist; membership in the American Society of Consulting Arborists (ASCA) is not required. However, membership in ASCA is for practicing arborists who specialize in advising, diagnosing, and recommending treatments, preparing appraisals, and offering legal testimony in court. Membership in ASCA signifies a high degree of professionalism in arboriculture and requires an academic foundation, extensive work experience, professional affiliations, and references. ASCA members need continuing education and the organization website (https://www.asca-consultants.org/) is searchable for current members. 

Certified horticulturist    

Certification by the American Society for Horticultural Science (ASHS). Minimum qualification are a combination of three to five years of experience or a combined level of experience and education in horticulture. ASHS certified horticulturists are skilled and knowledgeable in all areas of horticulture. 

Horticulturist    

Bachelor of Science (BS), Master of Science (MS), or doctorate (Ph.D.) in horticulture. The discipline in horticulture most related to tree care is ornamental or environmental horticulture. 

Certified forester    

Certification from the Society of American Foresters for professional competency of foresters. Certified foresters assist in evaluating options for your forest. Requires education or experience in forestry, and continuing education units. 

Forester    

Bachelor of Science (BS), Master of Science (MS), or doctorate (Ph.D.) in forestry. This education includes management of forests and wildlands to preserve natural resources, produce wood, and manage recreation in these spaces. 

Landscape architect    

Bachelor of Science in landscape architecture and state license. Specialize in landscape planning, design, and construction, no experience in horticulture or tree care is required. 

Landscape designer    

No license or certification is required. General knowledge of landscape design, construction, and species selection. 

Master Gardener    

Volunteers trained and certified by the University of Arizona Cooperative Extension or by other land grant universities. They provide home horticulture and gardening advice through County Cooperative Extension offices as a public service.

• Anderson L.M. and H.K. Cordell. 1988. Influence of trees on residential property values in Athens, Georgia (U.S.A): a survey based on actual sales prices. Landscape and Urban Planning 15:153-164.
• Fazio, J.R. How to hire an arborist, Tree City USA Bulletin No. 6.
• International Society of Arboriculture. 2011. Why hire an arborist?
• Wolf, K.L. 2007. City trees and property values. Arborist News 16:4:34-36.