It is important to check for ISA arborist certification. Certified Arborists are experienced professionals who have passed an extensive exam which covers all aspects of tree care. To maintain certification, arborists must earn Continued Education Units by completing exams, attending professional seminars, or donating their services to affiliated organizations. Check for membership in professional organizations such as the International Society of Arboriculture, Tree Care Industry Association, and the American Society of Consulting Arborists. Such memberships demonstrate a commitment on the part of the arborists to stay current on technques and safety information.