The leader has a ruler or tape measure. Each student has a piece of string ideally; or anything improvised – such as a belt. Students choose a tree; measure it with their string; come back to the leader to get the actual measurement; then work out the age of the tree 🙂

Broadleaved trees such as oak, ash, beech and sycamore put on about 1.5–2cm in circumference or girth per year. In open conditions, such as parkland, the growth rate will be nearer 2.5cm annually. So by measuring the trunk circumference and dividing by 1.5, 2, or 2.5 you can get a good idea of age. This method is known as ‘Mitchell’s Rule’, named after the late world-famous UK tree expert, Alan Mitchell.

Conifers commonly show a regular pattern of growth, producing a whorl of branches each year. So if you follow the main trunk up, you can see a whorl of branches all radiating out from the trunk at the same level, followed by a clear section, then another whorl and so on.