Jan Bostwick, age 12, of Rutland, Vt., for her question:

HOW OLD DO TREES GROW TO BE?

The normal age span of trees is different for each species. Some birch trees, as an example, normally die after 40 years of life. On the other side of the scale are the bristlecone pines that are still living after 4,500 years. They are, as a matter of fact, the oldest living things on earth.

The sugar maple tree frequently lives as long as 500 years. And some oaks live as long as 1,500 years.

Other long living trees incude the junipers and the giant sequoias.

Junipers live to be 2,000 years old while some of he sequoias have been around for 4,000 years.

There are about 20,000 kinds of trees on earth. More than 1,000 kinds live in the United States.

About 300 million years ago there were whole forests of trees unlike most of the trees that grow today. They have become extinct. The oldest known surviving order of ancient trees is the ginko, often called the maidenhair tree.