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 which 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 only be done by those trained and equipped to work safely in trees. Certified Arborist List
 

Services That Arborists Can Provide

Arborists can provide a variety of services to help maintain your valuable investment.

1. Pruning---The arborist can determine what type of pruning is necessary to maintain or improve the health, appearance and safety of your 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.
   • Thinning or removal of unnecessary branches.
   • Improving the shape or silhouette of the tree.
   
2. Removal---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. Arborists have the skills and equipment to safely and efficiently remove trees. Removal is recommended when:
   • The tree is dead or dying.
   • The tree is considered irreparably hazardous.
   • The tree is causing an obstruction that is impossible to correct through pruning.
   • The tree is crowding and causing harm to other trees.
   • The tree is to be replaced by a more suitable specimen.
   • The tree should be removed to allow for new construction.
3. Emergency Tree Care---Storms may cause limbs or entire trees to fail, often landing on homes, cars, other structures or other trees. The weight of storm-damaged trees is great and they can be very dangerous to remove or trim. An arborist can assist in performing the job in a safe manner, while reducing further risk of damage to your property.
4. Planting---Some arborists plant trees and most can recommend what types of trees are appropriate for a specific location. The wrong tree in the wrong location could lead to future problems due to limited growing space, insects, diseases, or poor growth.
5. Other Services---Many arborists also provide a variety of other tree care services including:
   • Practicing 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

There are a variety of things to consider when selecting an arborist which include:

• Membership in professional organizations such as the International Society of Arboriculture (ISA), the National Arborist Association (NAA) or the American Society of Consulting Arborists (ASCA) demonstrates a willingness on the part of the arborist to stay up-to-date on the latest techniques and information.
• Check in the phone directory yellow pages for those arborists who advertise as ISA Certified Arborists or display the official logo of the ISA Certified Arborist. 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 will have personal and property damage insurance as well as workers compensation insurance. Many homeowners have had to pay out large amounts of money for damages caused by an uninsured individual claiming to be a tree expert. You could be held responsible for damages and injuries that occur as a result of the job.
• 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 law that governs 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 worksites 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!
• Unless you know and are comfortable with the arborist, get more than one estimate. You may have to pay for the estimates, and it will take more time, but it will be worth the investment.
• Be wary of individuals who go door-to-door and offer bargains for performing tree work. Most reputable companies are too occupied to solicit work in this manner. Improper tree care can take many years to correct itself and in some cases never corrects itself. Are you willing to take that risk with your valuable investment?
• Good arborists will only perform accepted practices. For example, practices such as topping a tree, removing an excessive amount of live wood, using climbing spikes on trees which are not being removed, and removing or disfiguring living trees without just cause, are unnecessary.
• Don't always accept the low bid. You should examine the credentials and the written specification of the firms who submitted bids and determine the best combination of price, work to be done, skill and professionalism to protect your substantial investment.
• Get it in writing. Most reputable arborists will 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 non-governmental, 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 at least three years experience and who have passed 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 should 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 yourself on some of the basic principles of tree care. ISA offers several other brochures in this series which discuss many of the basic principles of tree care.

Why Hire an Arborist
Benefits of Trees
Buying High-Quality Trees
Insect and Disease Problems
Mature Tree Care
New Tree Planting
Tree Selection
Plant Health Care
Recognizing Tree Hazards
Trees and Turf
Avoiding Tree & Utility Conflicts
Tree Values
Why Topping Hurts Trees
Pruning Young Trees
Pruning Mature Trees
Avoiding Tree Damage During Construction
Treatment of Trees Damaged by Construction
 

Your local garden center, county extension agent or city arborist are also excellent sources of information if you should have further questions. They may also be able to refer you to certified arborists.

This brochure is one in a series published by the International Society of Arboriculture as part of its Consumer Information Program. You may have additional interest in the following titles currently in the series: Insect and Disease Problems; Mature Tree Care; New Tree Planting; Trees and Turf; Benefits of Trees; Tree Selection; Plant Health Care; Avoiding Tree and Utility Conflicts; Recognizing Tree Hazards; Why Hire an Arborist; Buying High-Quality Trees; Tree Values; Pruning Young Trees; Pruning Mature Trees; Why Topping Hurts Trees; Pruning Young Trees; Pruning Mature Trees; Avoiding Tree Damage During Construction; Treatment of Trees Damaged by Construction.
 

Developed by the International Society of Arboriculture (ISA), a non-profit organization supporting tree care research around the world and dedicated to the care and preservation of shade and ornamental trees. For further information, contact: ISA, P.O. Box 3129, Champaign, IL 61826-3129, USA.

© 1995 International Society of Arboriculture.
UPDATED FEBRUARY 2000