American chestnuts strive to survive

Ken and Jennifer Warthen, of Frederick, stand next to an American chestnut on their property that displays some natural resistance to the chestnut blight. The tree is 12 inches in diameter and about 50 feet tall.

The American Chestnut tree (Castenea dentata) was once the most dominant tree found in Eastern forests. In some areas, 1 in every 4 trees were chestnuts.

At its prime, there were nearly 4 billion chestnut trees found in the Eastern forests. This straight, fast-growing tree approached 150 feet in height and 5 to 10 feet in diameter. The majestic chestnut was prized for its timber, which was strong, straight and very rot-resistant. All of that changed with the introduction of chestnut blight (Endothia parastitica), a fungal disease that was first identified at the Bronx Zoo in 1904.

This wind-borne affliction quickly spread throughout the native chestnut range, and by 1940 most American chestnuts had been wiped out. Today it is estimated that less than 100 of the 4 billion original chestnuts are still alive.

Credit: - Mike Kay

In diseased trees, although the upper portion of the tree died, the root system remained alive in many cases. These root systems continue to send out sprouts that will grow for about 20 years until they become reinfected and die back to the ground.

American chestnut sprouts are not uncommon in Frederick County, but finding a large, healthy American chestnut tree is a rare occurrence. Our native chinquapins and post oaks are also affected by the chestnut blight, but it is not lethal to them.

The Chinese chestnut (Castenea mollissima) has a natural resistance to the chestnut blight, and it is thought that the importation of this tree brought the blight over to our shores.

Chinese chestnut is a medium-sized tree with a large spreading crown. It's the "chestnut" tree that is most often planted in groves or in a landscape setting for their nuts.

There are a number of active programs to re-establish American chestnuts, most of which are being coordinated by the American Chestnut Foundation. Most of these programs attempt to breed resistance into chestnuts by crossing American and Chinese chestnuts. There are a number of chestnut orchards and plantations located throughout Frederick County being tended by volunteers.

Another way chestnuts can become more resistant to the blight is to develop a natural immunity, called hypovirulence. In some cases this natural resistance occurs as a result of a virus attacking the blight.

Article by FCFCDB

Nature Notes for 8/7/2011