More about estimating the age of a tree
How to estimate the age of a living tree
It is possible to get a rough age estimate for a big old tree by measuring round its trunk (its girth) and using a ‘growth factor’. This approach does not work for young saplings.
The rate at which a tree grows will depend on:
which species it is
the soil (deep/shallow, well drained/waterlogged, nutrient rich/poor)
how much competition it faces from other trees.
Trees in the open grow faster than those in a wood because there is less competition from other trees, for light, water and nutrients.
At Long Meadow the big trees are of the following species: Ash, Sycamore, and Horse chestnut. All these species grow fairly slowly in maturity so have similar typical growth rates. Something like a willow, by contrast, grows at a faster rate and an oak tree more slowly.
At Long Meadow there are big horse chestnut trees in an avenue behind the Park Lane hedge – this is in the open. There are also small woods of ash and sycamore, for example the Spinney beside the brook (Award Drain).
As the procedure of estimating the age of an old tree is rather rough it is very helpful to consider what other information we can use to improve/check our estimate.
We do not know precisely when, but can guess that the Rowleys might have planted the horse chestnut avenue in the 1840s because the avenue trees were big enough in 1886 to be shown on the OS map. The present Abbey Farm house was finished in 1847 (plaque on house), so possibly the trees were planted as part of a makeover!
If the trees were planted in 1840, a few years after Queen Victoria was crowned, they would now be 182 years old.
It is possible to get a rough estimate of the age of a tree by measuring its girth (circumference) at about 1.5 m height above the ground.
Two horse chestnut trees in the avenue were measured in 2022. One had a girth of 3.9m, the other 4.1m. This shows why the approach is rough – both will have been planted at the same time as part of the avenue, and will have experienced very similar conditions over their long life, and yet they are not the same size. It is best to measure more than one tree in a group and take an average girth for the calculation.
There are a number of methods to be found online. For the quiz we have used two sources. The first, and simplest is from Outdoor and Woodland Learning Scotland:
The second, and more complicated is from the Forestry Commission:
Assuming a 4m girth the simpler method gives an estimate of 213 years and the Forestry Commission method an estimate of 188 years. So these methods suggest that the trees are about 200 years old.
How to estimate the age of a tree that has been cut down
Last December we had to fell a number of trees for safety reasons. We are therefore in the unusual position of being able to estimate the age of a tree by looking at tree rings.
We are going to look at the stump left when a mature Ash tree (‘T29’ in orange paint on the stump) in the Spinney was felled. Be careful if you go to look at it as it is right beside the brook (Award Drain).
What are tree rings? They are a record of the annual growth cycle. The rings show up because the tree grew fast in spring and early summer each year and more slowly each autumn. The fast spring growth looks light and the slow autumn growth looks darker. If conditions are good for growth (warm, regular rainfall) then the ring that is formed will be wider than that created in a year where the tree struggles for water, or it is cold.
At the time it was felled T29 was a big tree similar to the other big trees still in the Spinney. As it grew each year it expanded the width of its trunk. We can see this as a series of rings from the centre – laid down when it was a mere sapling – to the bark where the most recent growth happened.
If you look at the picture below you will see a slice of the T29 stump from the core to the bark and a blow up picture of a small section of the ring sequence. We have counted the rings in this blow up section – it represents 22 years of growth.
The blue rectangles roughly mark out more 20 year periods, from which we estimate the age of T29 as about 140 years.
For interest, the girth of the stump (not actually 1.5m above ground level) was 2.0m. Using this image below, you could have a go yourself.
Mark on the photograph the rings that correspond to the year when you were born, when your parents were born, and perhaps even when your grandparents were born.