This
'nuts and bolts' approach to tree
valuation seems to make the most
sense, but doesn't always apply
in today's world. Using this
method, tree value is
established by filling in
several parts of a mathematical
formula which takes into
consideration key factors about
the tree. Most of these factors
are expressed in the formula as percentages.
Three key factors are the tree
species, location and condition.
Species
Some tree species
are 'weedy' varieties and have
much less inherent value than
desirable ornamentals or quality
hardwoods. For example, a Black
Locust doesn't have near the
species value of an Oak.
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 |
|
 |
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White
Oak is top rated
with
100% in species
value |
|
Black
Locust only rates
30% in species value |
Location
The old saying
in real estate values is
"location, location, location."
That adage also applies to tree values.
A well placed specimen tree in the center
of your front yard has much more
location value than one that is
located in native woodlands out
in a rural area.
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 |
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 |
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A
specimen tree in the
front yard
is worth 100%
location value |
|
A
tree in the woods
would only
have a 30% location
value |
Condition
This factor
takes into consideration the
overall tree condition relating
to structure, wounds, roots and
anything else affecting tree
vigor and health. A tree with an
open wound on the trunk is worth
much less than a healthy one.
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 |
|
 |
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This
open cavity would be
cause for
deduction in
condition percentage |
|
This
tip dieback would be
cause for
deduction in
condition percentage |
Basic value of trunk size
Large trees
The
other key part of this formula
is a dollar amount which is
plugged-in to represent the
basic value by using the tree's
girth. On large trees this
figure is usually expressed as
the number of
"cross sectional square inches."
To find the cross sectional area
of a tree trunk, use the same
formula you used in high school
math class to find the area of a
circle:
3.14 times Radius squared (pr²)
Trunk diameter on large trees is measured at "breast height"
which is 4-1/2 feet above the
ground, and is more
commonly referred to as DBH or
Diameter
Breast Height. To
find the diameter of a tree,
wrap a cloth tape measure or
piece of string around the tree, and
divide that length by 3.14.
Once you have the diameter, you
can divide that length by 2 to
find the radius.
Radius
= ½ Diameter AND
Diameter = Radius times 2
Small trees
Smaller nursery-sized trees that are readily
transplanted are usually
measured by their "trunk
caliper" (diameter) anywhere from 6 to 12
inches above the soil surface,
depending on their caliper size.
Example: a 2
to 2-1/2 inch caliper tree is
measured 6 inches above the
ground.
Percent of Damage
In
the case of valuing a tree that
was damaged but not killed, it
is necessary to establish the
percent of damage to the tree.
This might apply in an instance
where an automobile leaves the
highway and strikes a tree,
breaking off some lower branches
and damaging part of the bark.
Or it could be a tree that split
in high winds, like the
flowering Pear in the photo
below. Even though half of this
tree is left standing, the
damage is extensive enough to be
considered a 100% loss.
Crunching the numbers
For
demonstration sake, our
imaginary tree has a species
value of 70%, a location value
of 80% and a condition value of
70%. It has experienced 30%
damage from an automobile
collision. The cross sectional
trunk square inch value at that
time was $26.00 and our large
18-inch DBH tree contains 254
square inches. Here's the math:
254
x $26 x .70 x .80 x .70 x .30 =
$776.63 loss
Summary
If a
tree is totally wiped-out and
can be replaced with a
nursery-sized transplant,
replacement value is fairly easy
to establish. However, when a
large tree is damaged, the trunk
formula method outlined
above is often used to
establish tree value. That being
said, the second method of
establishing loss of value is
tied to real estate value and
discussed below.
