The Age of a Tree by Alan Oliver an FoDNW member

The Age of a Tree

How old is a tree and how long is a piece of string? The answers to these two questions are, somewhat surprisingly, interconnected.

I have often wondered about the ages of the large oak trees in Darrick Wood and, in particular, the one in the roadway leading to the swimming baths which my wife and I pass by every day when taking our dog for a walk.

I knew that a tree’s age could be calculated by counting its rings but as chopping down one of our oaks wasn’t really an option, I decided to investigate whether there was any other way.

As is invariably the case these days the internet had the answer, or rather several answers, all of which involved measuring the circumference of the tree – hence the piece of string. With the aid of a trusty assistant (my wife in this case) holding one end of the string stretch it around the trunk at about shoulder height and then measure the relevant length of the string with a tape measure. You should then divide that figure by the rate at which the tree grows each year (the website shows the growth rates for various different types of tree; in the case of an oak it gave a figure of 1.88 cm per year).  Using this method I calculated the age of the oak in the baths road at approximately 160 years.

This method will give you a rough estimate of a tree’s age but the growth rate of an individual tree apparently depends on a number of factors including the proximity of water, the nutrient base of the soil and competition from trees nearby.

I tried this method of calculation out on a fir tree in our garden which I know the previous owners planted as a rooted Christmas tree in the mid 1970’s (it is now over 40 feet tall) and the result was certainly pretty accurate.

I have tried, without success, to find a significantly larger and hence older oak in the Wood than the one in the baths road but if anyone knows better why not get to work with your piece of string!