People ask what a tree is worth for very different reasons. Some are curious what a mature tree adds to their property. Some want to know what a tree gives back to the environment each year. And some have had a tree damaged by a storm, a contractor, or a neighbour and need a number for an insurance claim or a dispute. Each question has a different answer, and mixing them up causes most of the confusion.
Appraised value is not the same as yearly benefit
Tools like i-Tree estimate what a tree contributes each year in things like stormwater interception and air quality. Our i-Tree walkthrough puts a western red cedar at about $35.80 USD per year. That is a yearly benefit, not what the tree is worth. An appraised value is a one-time estimate of a tree's worth as part of a property, and it is the figure used in insurance claims, damage disputes, and development planning.
How an arborist puts a number on a tree
For larger trees, appraisers use the CTLA Trunk Formula Method from the Guide for Plant Appraisal. It starts with the cross-sectional area of the trunk, multiplies it by a unit cost, and then adjusts for the tree's species, condition, and location. For small trees, the more practical approach is replacement cost: what it would take to buy and install a comparable tree. At Arbutus we use the trunk formula for larger trees and a direct replacement formula for small ones, typically those under about 4 inches in trunk diameter.
What moves the number
The trunk drives the formula, which is why an appraiser measures it instead of asking how tall the tree is. Species is rated because trees differ in landscape value. Condition covers health and structure: a well-formed, well-cared-for tree is worth more than one with decay, poor structure, or obvious neglect. Location matters too. A single tree that anchors a home yard is worth more than one of many trees in the middle of a forest.
Two appraisers can land in different places
A formula sounds like it should give everyone the same answer, but it doesn't always. In a 2015 study, 14 certified arborists each appraised the same ten trees using the CTLA method. For any one tree, the results scattered by roughly a fifth to two fifths of the average value. Most of that variation came from two judgment calls: how the trunk was measured, especially on multi-stem trees, and how the tree's condition was rated. The study was small and done at a single arboretum, so it shows where the method is sensitive, not how far off every appraisal will be. It is a good reason to ask how a number was reached. A sound appraisal shows where the trunk was measured and why each rating was chosen.
When you need a formal appraisal
Insurance claims after storm damage, disagreements over a tree damaged by a neighbour or contractor, and planning around construction are the usual reasons. If a claim or dispute is involved, ask who will sign the appraisal and which method they used.
Keep records of your trees
Photograph your trees from time to time and keep notes on pruning and care, the way you would document other valuables. It is much harder to assess a tree's condition after it has been damaged, and dated photos help.
Need a valuation? Our Arborist Reports page covers tree valuation and cost estimates, or you can contact us.
Sources:
Komen, J., & Hodel, D. R. (2015). An analysis of the field precision of the CTLA Trunk Formula Method. Arboriculture & Urban Forestry, 41(5), 279–285. https://doi.org/10.48044/jauf.2015.026
Council of Tree and Landscape Appraisers. (2018). Guide for plant appraisal (10th ed.). International Society of Arboriculture.
