How can you tell the age of a tree?

An expert woodsman can guess the age of a tree, just by looking at it. He can be fairly sure that it took a leafy white oak tree 30 years to grow its full height of 120 feet. It took the tree perhaps another 20 years to widen its sturdy trunk and grow its thick, gnarled branches. The tree could be 50 years old, but this is only a rough guess. The expert needs more information before he can tell the exact age of the old oak tree.

If you study the leafy trees, you soon can learn how tall each one can grow. The American elm can reach up 100 feet, the slippery elm can grow only about 4.0 feet tall. The douglas fir can grow 120 fsat and the California redwoods can grow 300 feet tall. It takes a certain number of years for a tree to grow its full height and when you know each kind a tree.
 But a tree does not die when the climb toward the sky is finished. It can go on living for years, perhaps centuries and it goes on growing all its life. Each year the trunk and the main branches become a little thicker, new twigs are added to the spreading boughs. A big oak tree with a wide hollow trunk may be 100 or even 200 years old.
If we could see inside the trunk of the oak tree, we could tell exactly how many birthdays it had had. If a woodsman cuts down a tree, we see a cross section of the trunk like a flat table top. It is ringed with light and dark bands from just inside the bark to the very center. These tree rings, one inside another, tell us the exact age of a tree. All we have to do is to count them, one by one.
A seedling tree is just a slender stem topped with a whispy twig. Each year it adds a ring of new woody cells around the outer rim of its stem
The new cells added in the summer, when food is plentiful., are large.  As cool, fall weather cuts down the food supply, the new cells made are  small and darker. Each year, then, a tree adds a band of lighter and darker wood around its trunk. Until it reaches its full height, the trunk grows taller every year. When it reaches its proper height, a tree continues to add a ring of new wood around its trunk and also to add new twigs on its spreading arms. By counting the tree rings inside the trunk, we can tell the exact age of any tree.
It is not hard to count the rings on a flat, freshly out tree trunk. But sometimes a woodsman wants to know tha exact agcy of a tree without cutting it down. He uses a boring too to take a core of wood from the inside of the trunk, A metal tube is tunneled through the bark straight into the wood and comes out with a sample like a long pencil. This sample has cut right through the tree rings and there they are in a row, ready for counting.