How to hire an arborist

A smiling Ed Gilman gives a talk on how to hire an arborist.

Dr Ed Gilman has been a mentor to us, both through his books on structural pruning, and through seminars we’ve attended in Canada and the USA.

This excerpt from his book “An Illustrated Guide to Pruning Trees” covers some of the factors to consider when hiring an Arborist – a trained tree-care professional you can trust.

In addition to his work on structural pruning, his research on hurricane damage in trees and nursery methods for developing strong and stable roots, has been groundbreaking. Over the course of his career he’s managed to change the entire tree care industry in North America and around the world.

by Edward F. Gilman, University of Florida

Arborists make a career of caring for trees in urban and suburban landscapes. They work for companies commonly referred to as tree experts, tree services, tree care, arborists, tree specialists and others. Here are a few tips for selecting a company to work with your trees.

  • Avoid arborists who advertise they top trees. Ask the arborists if they will top your trees. If they say yes, do not use them. See Why Topping Hurts Trees (PDF via
  • Have one or more arborist look at the job, and get a written proposal specifying the work to be done. Consider paying an arborist to write specifications so you can give them to the prospective companies.
  • Ask for and check local references.
  • Be sure the company has the appropriate licenses, insurance, and certifications. Some communities require special permits, insurance, or certifications for all arborists to practice in the community.
  • Ask them what the ANSI A300 pruning standard and the ANSI Z133.1 safety standards are. Ask if their practices will be in compliance with these two standards. (Ask the same questions about the Nova Scotia or New Brunswick Occupational Health and Safety Acts and Regulations)
  • Ask them what tree book they have read most recently.
  • Ask them what seminar they attended most recently and when it was held.
  • Beware of an arborist who suggests removal of living trees. Removal of living trees is sometimes necessary, but should usually be considered the last resort after all other options have been considered.
  • Determine if the arborist is certified with the International Society of Arboriculture in Atlanta Georgia. Certified arborists must pass a written test and maintain certification by regularly attending classes. Except for registered consulting arborists with the American Society of Consulting Arborists, membership in other organizations is useful, but no tests or training are required for membership. Members simply pay dues to belong.
  • Ask for verification of personal and property liability insurance and worker’s compensation (or a waiver of worker’s compensation).
  • Low price is a poor gauge of a quality arborist. Often the better ones are more expensive because of more specialized equipment, more professional training, and insurance costs.
  • Know if your state, (province) or municipality requires a specific license or certification for providing these services.