How can we tell a tree's age?

You know how old you are because you count your birthdays. But a tree cannot talk and has no candles. So how can we find out how many years a tree has lived? The answer is hidden right inside its trunk.

A new ring every year

Each year a tree grows a little wider by adding a fresh layer of wood just under its bark. This layer makes a round line called a tree ring. One new ring appears every single year, like adding one more circle around a circle.

Counting the circles

If a tree is cut down, you can see all the rings on the flat end of the trunk, like a target made of wavy circles. Count the rings from the middle out to the bark, and that number tells you the tree’s age in years. Twenty rings means the tree was twenty years old!

Rings tell stories too

The rings can share even more secrets. A wide ring grew in a warm, rainy year when the tree had lots of water and sun. A thin ring shows a hard, dry year. So the trunk is like a diary, keeping notes about the weather long ago.

Wonder fact: Scientists can read tree rings without cutting the tree — they take a thin straw of wood with a special tool, and the tree keeps growing!