• 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 penetration
• Improving the shape or silhouette of the tree

Removal

• is considered 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
• is located in an area where new construction requires removal
  

• 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
When selecting the right 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 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 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 in arboriculture.