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 only be done by those trained and equipped to work safely in trees.
ISA Certified Arborist List
Services That Arborists Can Provide
1. Pruning - The arborist can determine
what type of pruning is necessary to maintain or improve the health, appearance, and safety
These techniques include:
• Eliminating branches that rub each other.
• Removing limbs that interfere with wires, building facades, gutters, roofs, chimneys,
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
• Training young trees.
• Removing limbs damaged by adverse weather conditions.
• Thinning or removal of branches to increase light penetration.
• 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.
• 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.
• Should be removed to allow for new construction.
3. Emergency Tree Care - Storms may cause limbs or entire trees to
fall, 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
• 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 including:
• Membership in professional organizations- such as the International
Society of Arboriculture (ISA), the Tree Care Industry Association, 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 worker's compensation insurance. Many homeowners have had to pay out large amounts of
money for damages caused by uninsured individuals claiming to be a tree experts. 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, it can never
be corrected. 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 that 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 that submitted bids and determine the best
combination of price, work to be done, skill, and professionalism to protect your substantial
• 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 experience 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 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.
Your local garden center, county 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 ISA
Developed by the International Society of Arboriculture (ISA), a non-profit organization
supporting tree care research around the world and is 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.
E-mail inquires: firstname.lastname@example.org