Last summer, the Guide for Plant Appraisal 10th Edition finally reached our industry. Long promised and fiercely debated, it addresses several changes in our systematic approach to placing a value to a tree. The new guide weighs looks, feels, and reads similar to the tree risk assessment manual. And this was intentional. As stated in the preface of the manual itself:
'[The] goal was to align the concepts and terminology of plant appraisal with those employed in the general practice of appraisal...similar to the International Society of Arboriculture’s effort to align tree risk assessment terminology with the general practice of risk assessment.'
A significant adjustment has been made by incorporating principles of real estate appraisal. This type of appraisal is now classified as a market approach. Some tree appraisers offer a specialized practice within the real estate appraisal community.
Other adjustments include different concepts of value, such as ecological benefits, or the value to the public. These concepts may be new to some of the plant appraisal community.
Of course, within the cost approach we still have the trunk formula method of appraisal, but we now call it the Trunk Formula Technique. And the way we derive values using a cost approach has been adjusted. Formerly we depreciated a tree through condition, species, and location ratings. Now we’ll be using physical deterioration (condition), functional, and external limitations.
We’ve got some handy new charts, forms, and formulas to use. And you’ll no doubt start seeing opportunities for continuing education in relation to tree appraisal. Foremost is a new Tree and Plant Appraisal Qualification (TPAQ) built around the new guide. It will be administered through the American Society of Consulting Arborists. The guide isn't intended to be a standard. But the information and concepts can generally be considered as a default position when conducting a tree appraisal.
A word of warning - the first edition has a few typos and errors. The tree appraisal community is still catching them. So be careful not to assume that you can find a copy of a form and instantly perform a tree appraisal. No doubt, a second revision will be needed before long.
In the meantime, each of the ISA chapters will be convening a new Regional Plant Appraisal Committee (RPAQ). The committee will be reviewing and updating the different species and planting costs. The goal of the RPAQ is to bring information we use into harmony with that of other chapters. We’ll endeavor to produce an accessible regional guide. It will be updated as cost data changes and new information becomes available.