One way to determine the age of a beech tree is by using a corer. A tree corer, an instrument made of a metal tube with two teeth at the opening and screw-like threads on the outer side, allows you to remove a small cross section of the tree trunk without seriously impacting the tree's health, according to Harvard University. Corer use requires some precision, however, in order to ensure you reach the exact center of the tree.
Position the corer as close to the ground of the beech tree as possible. Apply strong pressure as you screw it clockwise into the tree trunk, aiming for the center. Bore in horizontally all the way to the center of the tree.
Once you think the corer is in the center, turn the corer a half of a turn counterclockwise to break off the core. Insert the core extractor into the outer opening of the corer tube.
Carefully pull the core from the corer, taking care to keep the bark on the core. Slide the core into a plastic straw to protect it during transport.
Remove the core from the straw and set in on a windowsill. Allow it to dry undisturbed for about a week.
Create a groove on a wooden slat that will hold the beech tree core. Glue the core into the groove. Let the glue dry and then sand the core with fine sandpaper so the cellular structure is clearly visible.
Count the rings on the core with the aid of a magnifying glass. The number of rings indicates the approximate age of the beech tree.