Kathryn Fisher, age 11, of Thornhill, Ontario, for her question:

How old is a fully grown California redwood tree?

A tree never stops growing throughout its life. Every season it adds a ring of new wood around its trunk and branches. Every season it adds new twigs and leaves, even when the center of its trunk is rotted and hollow. The California redwood is a magnificent giant that grows on the slopes of the Far Western mountains. As long as it stands, every year it grows a little higher and adds a little to the width of its trunk.

The splendid tree grows slowly and after many centuries, the lower branches begin to fall from the trunk. The lowest branches of an ancient redwood may be 100 feet above the ground. Slowly through the centuries, the tree reaches 200, then 300 feet and the rusty red trunk may become 12 feet wide. The ancient tree may live on through 1000 and then 2000 birthdays. Chances are, it may be living and still growing after 2500 years.