CHARLESTON, W.Va. -- After reading about this website in several gardening publications, I had to visit and test this out on the trees in my yard.
At the Morton Arboretum's website (www.treetalk.mortonarb.org/areas-of-interest/do-you-know/how-to-tell-a-trees-age/556/), plant conservation biologist Marlin Bowles discusses a newly developed aging chart, adding, "the life histories of the region's old-growth trees are just a measurement away."
Bowles, along with research associate Michael Jones, cites work from a 1996 study of Chicago Wilderness' old-growth forests. The two calculated the age of trees in Chicago region forests by collecting core samples from about 600 area specimens. The cores provided rings for Bowles and Jones to count without harming the tree. The extractions were only 3/16 of an inch wide so the trees' living tissue was minimally affected.
According to the Morton Arboretum website, Bowles says old-forest trees can help nature enthusiasts learn more about the history of their local environment. For example, an area with mostly young trees must have experienced a major logging or fire event that would have eliminated all the older trees. On the other hand, a stand of very old trees means that there has been nothing for a long time to disturb the tree stand.
Here's how to calculate a tree's age. Bowles adds that it helps to have a little botany background and some math skills. (If I can do this, anyone can!)
First, identify the tree species (a tree field identification guide will be helpful). Next, measure the tree's circumference with a tape measure. Wrap the tape around the tree at chest height (4 to 5 feet up) to produce an accurate measurement. Divide the circumference measurement by pi (3.1416) to yield the tree's diameter. Check the accompanying chart to determine the specimen's age.
This measurement technique is about 90 percent accurate for forest-grown trees listed on the chart.
Some trees, because of poor growing conditions, may grow more slowly and, therefore, may be older than their size would suggest. On the other hand, trees grown in the open, like those in a suburban backyard, will be much younger for their size because the added sunlight available to them speeds their growth. Also, as the chart shows, different species grow at different rates.