Sources for More Information

Bulletin #15: How to Recognize–and Prevent–Hazard Trees

Some excellent publications are available that expand on the material presented in Bulletin No. 15. Here are two books that we recommend:

  • A Photographic Guide to the Evaluation of Hazard Trees in Urban Areas
    by Nelda P. Matheny and James R. Clark

    This is a very thorough treatment of a very important topic. This 72-page book is well illustrated and presented in a style that is easy to understand. Evaluation methods and forms are included, and a description of structural failure histories for over 100 species and cultivars. Available from

    P.O. Box 3129
    Champaign, IL 61826-3129
  • Tree Risk Management
    by E. Thomas Smiley, Bruce R. Fraedrich and Neil Hendrickson.

    50 pages with illustrations. This how-to publication includes the results of research that can be used in helping to decide if decaying trees are still safe, or more likely to fail. Available from

    Bartlett Tree Research Laboratories
    13768 Hamilton Road
    Charlotte, NC 28278


Probably no other single individual has done as much research and public education about understanding tree decay and hazards as the late Dr. Alex Shigo, former chief scientist and project leader with the USDA Forest Service. His various publications and other materials are now available online. Of particular interest here is his leaflet, Tree Hazards–13 Questions That Could Save a Life. For more information, please visit

Shigo and Trees, Associates LLC
PO Box 2466
Snohomish, WA 98291-2466
Phone: 360-862-1869
Fax: 360-862-8490

Also available online.

Magazine Article

Tree Risk Assessment–What We Know and What We Don’t Know is an excellent article by Nelda Matheny and Jim Clark that appeared in the February, 2000 Arborist News. Fortunately, it is also provided online by the International Society of Arboriculture.

Risk Assessment Course and Exam

The Pacific Northwest Chapter of the International Society of Arboriculture has been a leader in providing arborists with extra training in tree risk assessment. Those who successfully complete a course offered by the chapter several times each year receive certification for this special activity and are listed at the chapter’s website.

More Information

Call 1-888-448-7337 Monday–Friday 8:00 AM to 5:00 PM CST

Tree City USA is an Arbor Day Foundation program in cooperation with:

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