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
- 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
- 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
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
- 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
Selecting the Right Arborist for the
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
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
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
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, 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
E-mail inquiries: firstname.lastname@example.org
(c) 1998, 2004 International Society of Arboriculture.
UPDATED JULY 2005
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: email@example.com
© 2007 International Society of Arboriculture.
UPDATED SEPTEMBER 2005