Earlier this year, the International Society of Arboriculture (ISA) announced its renewed commitment to the Council of Tree and Landscape Appraisers (CTLA) and its collaboration on development of an eleventh edition of the Guide for Plant Appraisal.

In preparation for development of the eleventh edition, a public review and comment period on the current, tenth edition, of the Guide is open. To encourage engagement from as many practitioners and interested parties as possible, the deadline for comments has been extended to Friday 28 February 2025. 

Founded in 1975 and reaffirmed periodically, the CTLA is a collaboration of organizations that share an interest in developing industry consensus methodologies for tree and landscape plant valuation as published in the Guide for Plant Appraisal editions. First published in 1957 under the title Shade Tree Evaluation, the Guide for Plant Appraisal is the most informative and comprehensive reference on current knowledge of the approaches, processes, and methods of amenity plant valuation.

Following the close of the public comment period, the CTLA’s Content Review Committee will assess all public comments in the spring of 2025 and outline a direction for the revision.

A draft eleventh edition could be expected as soon as 2027 and will itself be subject to a public comment period prior to any publication. This aims to ensure openness for all parties who are directly and materially interested in providing input on the Guide. The Content Review Committee will again assess the comments and revise the draft as appropriate. The eleventh edition of the Guide for Plant Appraisal could be published as soon as 2029.

The current edition of the Guide for Plant Appraisal is available for purchase in digital and print format through ISA’s online web store. Inquiries regarding the Guide for Plant Appraisal or the Council of Tree and Landscape Appraisers can be directed to [email protected].