Just How Old is That Tree?

Since it?EUR??,,????'???s not polite to ask, you might have to estimate?EUR??,,????'???

It?EUR??,,????'???s easy, albeit time consuming, to tell the age of an old, downed tree when walking through the woods. Just count the tree rings!

However, this method just doesn?EUR??,,????'???t suffice when a tree is still standing, alive and healthy. Sure, increment cores can be elicited using increment borers, but this could cause injuries to trees. So how to tell the age of that huge white oak shading one of your projects without harming it?

The Athens-Clarke County Community Tree Program has released a method for estimating the age of trees with a few simple measurements and equations. Using the criteria below, you can measure your tree without affecting its health.

Step 1.

Measure the tree trunk?EUR??,,????'???s circumference in feet and inches at about 4.5 feet above the ground. For example, we?EUR??,,????'???ll consider a tree that is 11 feet, 9 inches around. This comes out to 141 inches, or 11 inches X 12 inches/ foot, then add 9 inches).

Step 2.

Next, you will calculate the diameter and the radius of the trunk (once again in inches).

To find the diameter, divide the circumference by 3.14 (pi).

Example: 141/ 3.14 = 45 in.
    Diameter = 45 in.

The trunk?EUR??,,????'???s diameter is referred to as the ?EUR??,,????'??diameter at breast height?EUR??,,????'??, or ?EUR??,,????'??dbh?EUR??,,????'??, and is a commonly-used measurement.

To find the radius, divide the diameter by two.

Example: 45 / 2 = 22.5 inches.

In accounting for the bark on the tree, deduct at least a half inch from the radius, and more (up to an inch) for very thick bark. For very thin bark, try subtracting less.

Example: 22.5 inches - .5 = 22 inches

Step 3.

Now you must figure out the average width of an annual tree ring for the species you are measuring. Ring-porous species have distinct annual rings that contain both late, or summer, wood rings (smaller vessels), and early, or spring, wood rings (larger vessels). Diffuse porous woods may have rings whose beginnings and ends are more difficult to discern. A magnifying glass may be necessary.

Tree ring width is dependent on several factors, including the age of the tree, the local climate conditions, genetics, the height above ground, the water and nutrient availabilities, insect presence, competition from other trees, and the tree?EUR??,,????'???s general health.

If other cross sections of the same tree are available, you can use this to help determine the ring width of your tree. Simply measure the radius of the cross section from the enter of the trunk to just inside the bark, count the number of rings, and divide the radius by the number of the rings. You?EUR??,,????'???ll end up with the average width per ring.

Example: 12 inches/ 60 rings = .2 inches/ ring.

Divide the number of rings by the number of inches to get the number of rings per inch.

Example: 60 rings/ 12 inches = 5 rings/ inch

Step 4.

Now to wrap it all up. Divide the radius of the standing tree by the average tree ring width to get the tree?EUR??,,????'???s approximate age.

Example: 22 inches / .2 = 110 years old!

Now you can compare the age of your tree with the average age of its species. While urban trees sometimes live shorter lives, some trees, under perfect conditions, can live for hundreds of year.