Measuring a tree
Trees submitted as nominees for the Big Tree Registry must be measured with circumference in inches, and height and crown spread to the nearest foot. The total of these measurements is the points awarded to a particular tree. A champion tree has accumulated the most points. If two trees of the same species have identical scores, the tree with the largest trunk circumference becomes champion.
Measure, to the nearest inch, the distance around the tree at a point 4½ feet up from the ground to get the circumference. A flexible tape measure is a good tool to use.
Help for hard to measure tree.
Height is the hardest measurement to obtain. The most reliable method uses a hand level or hypsometer. If these instruments are unavailable, use a ruler and follow the instructions below.
- On a 12-inch ruler, mark the 1-inch and 10-inch lines with tape.
- Work in pairs to measure height.
- Person A stands at the base of the tree.
- Person B, while holding the ruler up in front of their eyes at arm length, moves back until they can see the whole tree from top to bottom between the 0-inch and the 10-inch mark on the ruler.
- Person B then moves the ruler until the base of the tree is exactly at 0-inches and the top of the tree is sighted exactly at 10-inches.
- Person B sights out from the ruler’s 1-inch mark to a point on the trunk above the base.
- Person A marks this spot on the trunk with tape.
- Measure the distance from the base of the tree to the 1-inch mark (X) on the tree.
- Multiply by 10 to get an approximate height of the tree.
3. Crown spread
- Setting a stake directly under the outside edge of the crown farthest from the trunk (A)
- Add another stake directly opposite it at the outer edge of the crown on an imaginary line passing through the tree’s center (B)
- Set stakes marking the shortest diameter of the crown passing through the center of the tree (C and D)
- Measure the distance between points (A) and (B)
- Measure the distance between points (C) and (D)
- Add the two measurements together and divide the sum by two to find the average crown spread. Average Crown Spread = [(Distance A to B) + (Distance C to D)] / 2
- Calculate one-quarter of the crown spread by dividing the average crown spread by four. One-quarter Crown Spread = Average Crown Spread / 4
A champion tree has accumulated the most points based on the measured circumference, height, and crown spread. If two trees of the same species have identical scores, the tree with the largest trunk circumference becomes champion.
Example: Red Pine (Pinus resinosa)
Circumference = 120 inches
Height = 126 feet
Crown Spread = 48 feet
Circumference = 120
Height = 126
Crown Spread = 48 ÷ 4 = 12
Total points = 120 + 126 + 12 = 258
Want more information about trees, visit Minnesota's Forest Treasures.