Oaklee loves pi
Time for another edition of Oaklee Does Math for Pie! Actually, it’s pi day so we’ve enlisted everyone’s favorite squirrel to teach you a bit more about how to use pi to estimate the age of a tree.
For this exercise, you’ll need a tree (forest grown trees work best — trees out in the open grow at different rates depending on site conditions), measuring tape, and a calculator.
Step 1: Identify your tree and find it on the list (below).
Step 2: Measure up to 54 inches from the ground (4 1/2 feet). This is Diameter Breast Height, or DBH.
Step 3: Measure around the tree at DBH to find the circumference in inches.
Step 4: Divide the circumference by the mathematical pi π (3.14). This will give you the tree’s diameter (we learned that last year, remember?).
Step 5: Multiply the diameter by the growth rate number listed next to your tree species in the chart. This will give you the approximate age of your tree! For example, a white oak with a circumference of 126 inches would have a diameter of about 40 inches. Multiply that by the white oak’s growth factor of 5, and you’ll find your white oak is approximately 200 years old.
C/π=d, where C is circumference and d is diameter
d*gr=age, where d is diameter and gr is growth rate number
|American beech||6||Norway spruce||5|
|American elm||4||Pin oak||3|
|Austrian pine||4.5||Red maple||4.5|
|Black cherry||5||Red pine||5.5|
|Black maple||5||River birch||3.5|
|Black walnut||4.5||Scarlet oak||4|
|Bradford pear||3||Scotch pine||3.5|
|Common horsechestnut||8||Shagbark hickory||7.5|
|Colorado blue spruce||4.5||Shingle oak||6|
|Douglas fir||5||Silver maple||3|
|European beech||4||Sugar maple||5.5|
|European white birch||5||Sweet gum||5.5|
|Green ash||4||Tulip tree||3|
|Kentucky coffee tree||3||White fir||7.5|
|Littleleaf linden||3||White oak||5|
|Northern red oak||4||White pine||5|
|Norway maple||4.5||Yellow buckeye||5|