Here’s a sample of how trees are valued. This is a simplified version of a professional arborist’s method and is not meant for legal or insurance purposes but it will give you a good idea of what your trees are worth.
In this simplified example we’ll use the Trunk Formula Technique (TFT) from the International Society of Arboriculture Guide for Plant Appraisal. The TFT calculation looks like this:
Reproduction Tree Cost = Largest Available Stock + Installation Costs
Basic Tree Reproduction Cost = (Cross-sectional area of the original tree) x ((Reproduction Tree Cost) / (Reproduction tree cross-sectional area))
where Cross-Sectional Area = Circumference2 x 0.0796
Depreciated Reproduction Cost = (Basic Tree Reproduction Cost) x (Condition) x (Functional limits) x (External limits)
For our example
Reproduction Tree Cost: $380 for coniferous, $480 for deciduous (new 3″ diameter saplings, delivered and installed) PNW-ISA Species Ratings for Landscape Tree Appraisal.
Basic Tree Reproduction Cost: The new trees are 3″ diameter so you can multiply the cross sectional area by $56.76 ($380/7.068) conifer or $67.91 ($480/7.068) deciduous.
Condition you observed (health, structure, and form):
Excellent: 1.0 – 0.9
Good: 0.9 – 0.75
Fair: 0.5 – 0.75
Poor: 0.30 – 0.50
Functional limits: trees located beneath power lines, near property lines, species that cause excessive litter, or species listed as invasive species. (For this example we are using 0.95)
External limits: City ordinances, easements, utilities, significant pests in the area, or site and climate changes. (For this example we assume your trees are in the Arnold Irrigation right of way and use 0.33)
Additional Costs: Site clean-up, site changes, irrigation, and future maintenance (for this example we assume these costs are zero because Arnold Irrigation cleans up the mess).
To value your trees
Evaluate the tree’s health and structure with binoculars for the crown and take a good close look lower down for dead limbs, bugs (sap dripping) and bark damage.
Measure the circumference of the tree at around chest height (4’6″) . Multiply that number by itself and then multiply that result by 0.7854. This is the cross-sectional area of your tree.
Now multiply that number by 57.76 for conifers (Pine or Juniper) or 67.91 for deciduous. This is what your tree is worth before depreciation, the Basic Tree Reproduction Cost.
The Depreciated Reproduction Cost (value of your tree) is the Basic Tree Reproduction Cost you just calculated multiplied by the observed condition, functional and external limits.
|Circumference measured at chest height||Cross Section Area||New Tree Factor||Condition||Functional Limits||External Limits||Tree Value|
Here are the appraisal calculations:
Tree 1 Conifer (Pine) Cross section area = 712 x 0.0796 = 401.26 Basic Reproduction Cost = 401.26 x 57.76 = $23,177 Depreciated Reproduction Cost = $23,177 x 0.75 x 0.95 x 0.33 = $5,449 Additional Costs = 0 (Arnold Irrigation will remove and clean up) Total Reproduction Cost = $5,449 +0 = $5,449 Appraisal Value = $5,400 (rounded to hundreds)
Tree 2 Deciduous (Aspen) Cross section area = 192 x 0.0796 = 28.74 Basic Reproduction Cost = 28.74 x 67.91 = $1,952 Depreciated Reproduction Cost = $1,952 x 0.6 x 0.95 x 0.33 = $367 Additional Costs = 0 (Arnold Irrigation will remove and clean up) Total Reproduction Cost = 0 + $367 = $367 Appraisal Value = $400 (rounded to hundreds)