The saga of the American chestnut (Castanea dentata) is one of life, death, and hopefully rebirth. Once numbering nearly 4 billion in North America and accounting for 25% of all the trees in the Appalachian region, mature specimens in this range are now estimated at fewer than 100, though there are several pockets remaining in the west. With trunks commonly measuring 4 to 7 feet in diameter (occasionally 10-15) and branches rising over 100 feet in the air, a forest of mature chestnut was surely an impressive sight. Economically, its importance cannot be overstated. Its strong, even grained wood was ideal for cabins and barns, fence rails, shingles and siding. Having a high tannin content, the wood is naturally rot resistant and supplied most of the railroad ties and telegraph poles that supported America’s westward expansion. Its bark provided a primary source of tannin to treat and cure leather. The nuts were an important resource as well, being a food source for the local people as well as livestock and wildlife. They were collected by the wagonload and sent off for sale in the bigger cities providing one of the few sources of cash for the local population many of whom were subsistence farmers. They really could be found for sale “roasting on an open fire” around Christmas time!

 

In 1904, the curators of the Bronx Zoo noted an unusual illness affecting its chestnut population. Cankers developed that ruptured the bark and ultimately girdled and killed the trees. This blight spread 50 miles a year killing every chestnut in its path. By the time the blight reached Pennsylvania, the federal and state governments were using every means available to halt the spread. Quarantine lines were cut but were quickly jumped by the blight. A variety of chemical controls were attempted but to no avail. As the situation appeared hopeless, lumber men scrambled to cut down any available trees to harvest the timber before it died and rotted. We will never know if this practice resulted in the loss of any naturally resistant specimens from the gene pool though that is certainly a possibility. It is estimated that between 1910 and 1950 3.5 billion trees were lost, making it one of the greatest ecological disasters in recorded history.

 

The blight that decimated the chestnut population was a fungus brought over from Asia, Cryphonectria parasitica.  The fungal spores are spread by wind or by birds and insects, and enter the tree through cracks in the bark or other wounds. The fungus grows in the cambium layer and the tree responds by forming a callus to try to wall off the infection. This causes the characteristic swelling and rupture of the overlying bark known as a canker. Unfortunately, the tree cannot contain the fungus and ultimately, the canker girdles the tree and everything above the canker dies. Interestingly, the trunk and roots below the canker remain alive and chestnut has the ability to send up sprouts from the root. To this day, one can frequently see immature chestnut trees in the forests of their former range. Unfortunately, they are attacked by the fungus by the time they are a few inches in diameter and almost universally are dead before they reach sexual maturity and the ability to flower.

 

This, however, is not the end of the story and it is not a story without hope. There are a number of organizations actively working to restore the chestnut to its former range. One such group is The American Chestnut Foundation. They are using a breeding program in which the American chestnut is crossed with the blight resistant Chinese chestnut. Blight resistant offspring are then back crossed with American chestnut. This is done 3 times and then blight resistant offspring are crossed with each other 3 times. This yields a tree that is genetically 94% American chestnut yet carries the genes for blight resistance. There are numerous test farms growing these trees throughout the Appalachian region and the hope is that in the not too distant future, these trees will be used to repopulate the natural range of the American chestnut.

 

The story of the American chestnut is a fascinating one. It’s also a rare opportunity to bring a magnificent tree back from the brink of extinction. If you would like to learn more about the American chestnut or contribute to the restoration efforts, contact The American Chestnut Foundation at www.acf.org.

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Thursday the 21st. Thanks for visiting Woodturners Unlimited.