Circumference is measured at 4.5 feet above the ground. If a growth or branch is located at this point, measure below it where the circumference is least. If the tree forks below 4.5 feet, measure the larger fork at 4.5 feet.
To measure the circumference, locate a point at 4.5 feet above the ground on the trunk and place the zero end of the tape there. The tape is wrapped around the trunk tightly without sagging so that it exactly meets the zero end of the tape. The circumference is read in feet and inches.
Crown Spread can be measured by setting a stake directly under the outside edge of the crown farthest from the trunk (A) and another directly opposite it at the outer edge of the crown (B) on a line passing through the center of the tree.
Next, set stakes marking the shortest diameter of the crown passing through the center of the tree (C and D). Measure both distances to the nearest foot with a tape measure.
Add the two measurements together and divide the sum by two to obtain the average crown spread.
Height is the distance between the base and the top-most branch of the tree.
Measure tree height like this:
- Make a target 5 feet tall. This can be a rod or a stake.
- Place this target against the tree, making sure that it will be visible as you walk back to measure it. Be sure the target is vertical or your reading will not be true.
- Take a yardstick. Cut a fine notch at each inch mark.
- Hold the yardstick vertically and back up from the tree to the point where the five-foot target exactly fills one inch on the yard-stick.
- Without moving the yardstick, sight from the base of the tree to the top of the tree. Note the number of inches on the yardstick filled by the tree.
- Each inch is equal to five feet. If the tree occupied 18 inches on the ruler, then 18 x 5 feet = 90 feet, the height of the tree.
Take measurements from several points around the tree and use an average of measurements for the height.