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I get this question a lot when someone damages a tree or a part of the landscape "what's the value of the damage?"
To answer that question the plants in general do have value and how that value is determined is based upon the current edition of the Plant Appraiser's Guide and its application. These assessments are made by a Certified Arborist with as current and accurate understanding the Plant Appraisal and a the arborist has had experience testifying in court or deposition under intense scrutiny
Appraising the Monetary Value of Landscape Plants
Landscape plants serve functional and esthetic roles in
rural, urban commercial, or residential landscapes.
Such plants have market value much like real estate,
but that value is often difficult to determine.
According to the Guide for Plant Appraisal, four primary factors help in assessing the value by the Cost Approach: Species, Condition, Size, and Location. These factors can be objectively evaluated, and can work additively to arrive at a dollar valuation. We will address these factors and explain how they influence a tree's value.
1. TREE SPECIES - Is this a good species for this area or for the site? Species Ratings vary geographically. The guidelines suggest that native species get higher ratings than imported species. Considerations include whether the species is tolerant of the climate, the soils, and the water availability. A 100% Species Rating could be given to an indigenous native tree tolerant of a site's environment. In Ohio and other states we have companion documents that provide these values based on the opinion of a committee of arborist. A low Species Rating would be given to a tree that is native to the Ohio, no matter its condition. On the other hand, a medium Species Rating would be given to a non-native tree that can tolerate extreme heat and compacted soil, and survive on scheduled irrigation. Some non-natives might get a moderately high rating because of their general adaptation to Ohio conditions. But this is a species by species issue.
2. TREE CONDITION - Does this tree have strong structural integrity and good vigorous health? The plant's existing condition is the most reasonable gauge for determining the Condition Rating. Even if the tree species is known to be weak or to be susceptible to insect infestations, we give the Condition as a "real time" assessment. We do not make allowances for the causes of the Condition rating. Issues like structural integrity includes the determination of root conditions and stability; trunk soundness, decay, or cavities; then branch conditions, soundness, and attachment. We consider tree structure in relation to its potential to fail and damage something. Plant Health and vigor can be evaluated by the annual shoot growth from preceding years. We also look at leaf discoloration and size, decay, dieback, disfiguration from disease or insects, etc. Problems with infrastructure will cause a lower rating. Insufficient room to expand, soil compaction from parked trucks, damage from construction and other "urban" issues can have an influence. Human-caused damage plays a part in reducing the value of a tree. We give the roots a rating for Structural Integrity and for Health. We do the same for trunk, scaffold branches, small branches, and foliage. Add scores, and convert to percentage to determine the Condition Rating. A tree that is dying back (regardless of reason) will have a lower Condition Rating than the same species which is not suffering. Comparing two of the same species, a more vigorous individual will rate higher than another. Age does not influence rating. A Heritage or Valuable tree might have any Condition Rating.
3. TREE SIZE - Is this tree large and imposing or small and full of potential? We compute two things: 1) cross-sectional trunk area of the tree in question, and 2) its dollar value. To link size to money, we compare trees on a site to "dollar per size unit" value of the same species for sale in a local nursery. In both the landscape tree and the nursery tree, trunk area is determined from circumference, and the trunk is considered to be a circle. The Guide to Plant Appraisal contains guidelines for measuring and formulas for determining multi-trunk areas, trees on slopes, leaning trees, etc. We determine the unit value for the landscape tree by comparing it with a nursery tree's value. If the nursery tree with 10 sq inches of trunk cross-sectional area sells for $300, we assign the landscape tree a value of $30 per square inch of trunk area. If the landscape tree has 50 sq in. of cross-sectional trunk area, its value is $1500. We have two answers: area and dollar value. If the tree is not available anywhere locally, we can go further afield to get prices. Trees that are not available at all can be measured for size and compared to others of their species, but not given a monetary value. Their rarity or history becomes more important. Based on trunk area, smaller recently-planted trees may be valued very close to the replacement cost. Older trees (same species), with diameters of over 6" will be geometrically more valuable as they increase in size. This is particularly true as tree size grows beyond the largest available box in local nurseries.
4. TREE LOCATION - How does the tree perform in the landscape? Location Rating is the average of three sub-ratings: Site, Contribution, and Placement. This helps determine how the tree has been designed into the landscape, how much it contributes, and whether it is "working" to enhance that landscape. We rate from 10 to 100% on the following. Site (relative market value within the city, county, region) implies that trees on a well-maintained site are worth more than the same species on an unkempt property. This implication is controversial. Money talks. Contribution (functional and aesthetic value) considers things trees do: shade, screening, dust control, cooling, defining vistas, crowd control, and all aesthetic and historic factors. Placement (can it perform its function?) addresses the design/siting of the tree so that it has the best chance to provide the shade, control the crowds, or screen the view. A tree that frames a building or blocks an unsightly view will get a different rating than one that does not. We average the three ratings to determine a final Location Rating for the tree.
Using the Cost Method of Plant Appraisal as defined in the Guide for Plant Appraisal, we make a calculation based on all of the ratings. 1. Assume the tree is larger than any tree in a nursery. The calculation of the value of a tree would begin by using the price of the largest size of the species available in the nursery trade. This is combined with a cost for installation to give a Installed Plant Cost. 2. We divide the Installed Plant Cost by the trunk area (in square inches) of the boxed nursery tree. This gives a $$ cost / sq inch for the nursery tree. 3. We multiply that $$ cost / sq inch of nursery tree by the Size of the tree in question. We have measured this in the field. This gives a hypothetical cost for a perfect full grown tree at today's prices. 4. We then multiply that value for the perfect full grown tree by all the combined percentage ratings from Species, Condition, and Location. Typically this reduces the value. The end resulting value creates the value of the plant that was lost or destroyed.
Cost of Repair
In some cases if the plant can be repaired by reasonable and industry approved means the cost of repair may be applied as well. This again can be determined by a qualified Certified Arborist.