How to Decide the Age of a Tree?

There are three simple methods to estimate the age of a tree −

• Method 1 − Measuring the Trunk

• Method 2 − Counting the Rows of Branches

• Method 3 − Counting the Rings on a Stump

The trunk of the tree provides the measurements. The circumference and the radius of the tree trunk help to estimate age. Counting the rows of branches of the trunk also indicates age. The rings inside the trunk also reflect age. It cannot reach the rings unless the tree is cut down. Use one or two methods to reach an accurate understanding of the age.

The materials needed are a measuring tape, a calculator, Internet for reference, and pen and paper for making notes.

Method 1: Measuring the Trunk

The first method to estimate the age of a tree is to measure its trunk accurately. For this method, you need to follow the steps given below −

Step 1

Measure the trunk circumference at the height of 4/5 feet above ground level. Pass the measuring tape around the trunk and carefully and accurately measure the trunk. If branches are below 4/5 feet, measure just below the branch level. If it is hilly ground, measure twice, uphill and downhill sides, and take the average.

Step 2

Use the circumference information to calculate the trunk radius and diameter. Divide the circumference by 3.14 to find the diameter. Half of the diameter is the radius. As an example, consider a circumference of 77 inches. The diameter will be about 24 inches. The radius will be 12 inches. They are rough calculations.

Note − Avoid including the bark in the measurement. According to the tree type and trunk size, consider the bark thickness. Some trees, like the black oak, have a thick bark. Birch has a thin bark. Reduce the measurement by half or one inch to deduct the bark.

Step 3

Look around, and you might find fallen trees of the same type nearby. If the rings can be seen, count the rings. Measure the radius also. Dividing the radius by the number of rings helps to understand the average ring width. For example, if the radius is 12 inches with 62 rings, the average works out to approximately half an inch.

Note − The tree species and the environment decide the rate of growth. Even if no nearby fallen tree is found, an estimate of the growth rate would be possible. Use the ring width and the growth rate to calculate the tree's age.

Step 4

Find information online about the species' average growth rate. Type the location, too, for a better estimate. One foot of trunk diameter usually means ten years of growth. In forests, growth is higher compared to town areas and congested forests. The circumference growth rate for beech and sycamore may be about half an inch yearly.

Step 5

The calculations were easy if found a stump or fallen tree nearby. Now you know the average ring width. Divide the radius of the living tree by the average ring width. Imagine that the radius was 12 inches and the average ring width was 0.10 inches. Dividing 12 by 0.10, the age works out to 120 years. 

After knowing the circumference −

• Divide it by the average growth rate.

• Imagine the circumference is 77 inches, and the growth rate is between 0.5 and 1 inch.

• Make two calculations.

• Divide 77 by 0.5 and 77 by 1.

The results are between 77 and 154 years old.

Method 2: Counting the Rows of Branches (whorls)

The second method is counting the rows of the tree branches. Let’s know the steps −

Step 1

Some tree species, like conifers, have rows of branches on the trunk. All the branches in the row are at the same height. This method is more exact than counting the rings. Yet, we can estimate the age without killing or injuring the tree. In conifers, the branches grow annually and regularly. It is easy to count the rows of branches in young conifer trees. In broadleaf trees, the growth is not regular and cannot properly decide the age.

Step 2

Start counting the rows of branches that grow together at the same height on the trunk. Start from the base of the trunk. The rows of branches are followed by the short length of the trunk and then the branches again. Count the whorls to the top of the tree. Sometimes irregular growth happens, like a single branch or two whorls growing very close together. Probably bad weather, a lightning strike, or other injury were responsible. These need not be counted.

Step 3

Among older trees, the trunk bottom may have stubs. Does the trunk below the first row of branches have any growth? If knots or stubs indicate earlier growth of branches, they should be counted. Imagine counting seven regular whorls. Below the first whorls are two stubs and one knot where branches once stood. Now the total stands at ten.

Step 4

Considering seedling growth, add three years to the tree's age. First came the germination and the seedling. That took three years before the branches commenced. Thirteen years would be the total.

Method 3: Counting the Rings on a Stump

It would help if you found an exposed stump where the rings can be seen. The total rings represent the years of existence of the tree. Among light and dark rings, one year combines one light and one dark ring. The dark rings are better seen so that you can count them quickly. The number reflects the age in years. Climatic conditions are also understood through the rings. Thin rings mean cold and dry years. Thick rings reflect good environmental conditions.

Step 1

Rings get clearer if you rub them with sandpaper. First, use rough sandpaper, followed up by fine sanding. A little moisture would also help. If the rings are crowded, use a magnifying glass to see better.

Step 2

The pith is the circular center of the rings. Count the total sets of rings visible on the stump. Start from the pith. Count till the bark. The bark may hide the last ring but count it too. Keep recording with pen and paper to avoid confusion with numbers. The total sets of rings, one light and one dark show the probable tree age, maybe fifty-five.

Conclusion

Enjoy the adventure amidst nature, whether in the town or the forest. Safety precautions are important in the forest. A lot of patience, care, and time is required to succeed. The estimates are only approximations. Online research according to the tree species and location would help you clarify some of your doubts. Plan and arrange the required materials well in advance, along with food and water for the outing.