Sources for More Information

Bulletin #15: Tree Risk Assessment — Recognizing & Preventing 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 Assessment — Recognizing & Preventing Hazard Trees
    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

Also available from the International Society of Arboriculture are numerous other important publications. These include:

  • Tree Risk Assessment Manual
  • ANSI A300 Tree Risk Assessment
  • Best Management Practices
  • Basic Tree Risk Assessment Form


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 U.S. 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.

Tree Risk Assessment Courses

Arborists and urban foresters now have the opportunity to expand their knowledge and training in the fundamentals of tree risk assessment by attending qualification courses offered in a number of locations. More information is available from the International Society of Arboriculture.

More Information

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

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