Looking up at trees

If you’re anything like me, you will have a sentimental attachment to certain trees in your life.

You might love a tree because you used to climb it as a child, or because it has the biggest and best conkers. It might be that you pass it every day on your way to work or when walking your dog.

My favourite tree is a hawthorn that stands at the side of our house. Every May, it brightens up our garden with its cheerful white blossom and is frequently visited by wood pigeons, great tits, blue tits, dunnocks and house sparrows.

If you want to learn wildlife identification skills, trees are a good place to start since they can’t run or fly away from you. Plus, at this time of year, it’s much easier to distinguish between species since they all have their leaves, many of which are quite different.

It’s an ideal 30 Days Wild activity; all you need is an ID guide, either in the form of a book or a printed off sheet from the internet.

Since I’m already pretty familiar with trees, for 30 Days Wild I decided to go one step further and find out how old some of the trees around me are.

There are a few methods for aging trees. The most well-known method is to count the number of tree rings in its trunk but this isn’t ideal for living trees – you’d have to cut them down to stumps. Luckily, there is a way of approximating the age of a tree that does it no harm – using the circumference of the tree’s trunk and its yearly growth factor.

Trees will grow at different rates depending on how good the soil, shelter or climate is and how much space and light they have, so this method for determining a tree's age is not exact.

To start, you need to measure the tree’s circumference, which is the distance around the tree’s trunk. You can use a sewing tape measure for this and take the measurement between 1m - 1.5m off the ground. Try to avoid any lumps and bumps in the trunk. If you don’t have a sewing tape measure you could use a piece of string and then measure that afterwards.

Once you know the tree’s circumference, you need to find out the tree’s average growth rate, and divide the circumference by the growth rate. You can research this information online, but below are some examples:

Species of tree      Growth of girth per year 
Average                              2.5cm
Oak and beech                 1.88cm
Pine and spruce               3.13cm
Sycamore                          2.75cm

I tried this out by measuring some of the trees near our office in Cuerden Valley Park. Always making an effort to make life more difficult, I picked some quite big trees, so I needed help reaching around the trunks, and I very nearly fell down a steep slope while measuring a sycamore but it was worth it.

That particular tree was approximately 73 – it was a new sapling when the Second World War finished.

One beech tree had a circumference of 184cm so I worked out that it is roughly 95-years-old (184 ÷ 1.88 = 95.7). To imagine that this tree was a young sapling in 1923, when Tutankhamun’s tomb was being unsealed, is quite sobering.

So for 30 Days Wild why not find out how old your favourite tree is? Don’t forget to share you findings with us on social media using the hashtag #30DaysWild