Photo by Bruce Marlin CC BY-SA 2.5 An American Chestnut tree.

Up until around 1900 the American chestnut (Castanea dentata) was among the most valuable trees in the forests of the eastern United States. It was not valuable because of its rarity, as it was also one of the most prevalent trees in the region. The American chestnut made up nearly one quarter of the standing trees in the Appalachian forest; from the mountains of West Virginia into the Georgia mountains, these magnificent trees covered the highest of mountain peaks.

The American chestnut was a fast growing tree, resulting in trunks neary six feet in diameter and over 100 feet tall. The wood of the chestnut was more useful than any other hardwood in America as it provided timber for houses, barns and fences. Its tannin was used in the leather industry and its nuts were excellent food sources for people and wildlife alike. The wood was popular because its straight grain made it easy to split and work with hand tools, and the heartwood of mature trees was very high in tannin content which made the wood rot and decay resistant. In fact many structures built with American chestnut are still standing today.

I know what some of you are beginning to think, because in society today everything is blamed on climate change and human disregard for the environment. Some of you think the American chestnut is nearly extinct because of over harvesting, but this is not the case. Up until a few years ago the tree was thought to have been extinct due to the chestnut blight, which was first documented in 1904 by a forester working at the Bronx Zoo in New York City. The forester noticed that all the American chestnut trees in the zoo were dying and began to research the cause. It turns out that a fungus, C. parasitica, was causing the disease in the trees. But where did this fungus come from and how does it spread?

As it turns out it was the result of human interaction that caused the blight, but it was not through necessarily negligent actions, but from a lack of knowledge. It is generally agreed that this fungus entered the United States along with Japanese chestnut trees that were being imported by orchards in the late 1800s. The Japanese chestnut grew for generations in contact with this fungus and as a result had developed a natural immunity to the fungus. The fungus produces two different kinds of spores, one that is easily spread by the wind and another that is carried by rain, insects and birds. These spores spread the infection south from New York at the rate of about 200 miles every ten years, killing almost every mature chestnut tree in the natural range of the American species. The blight reached Georgia in the 1940s. The fungus attacks the phloem tissues and water-conducting cells of the tree, and once the phloem dies in a complete ring around the stem, the tree can no longer transport water to its leaves and rapidly dies.

The American chestnut can still be found in the Eastern forests today, but it is no longer the majestic tree it once was. Modern American chestnuts rarely reach thirty feet, or even begin to produce nuts before the fungus attacks and kills the tree. This same fungus also infects the Allegheny chinkapin and some species of oaks. The good news is that now that we know the cause and have more advanced scientific technologies in plant genetics, we have a chance to recover the once majestic tree. The American Chestnut Foundation is utilizing a backcross breeding program by introducing genes from the resilient Chinese and Japanese chestnut to generate resilient hybrids.

The program is approaching the problem from two angles, one is making the tree more resilient through backcross breeding and radiation treatments on the seeds to form blight resistant mutations. The second angle is the investigation of the hypovirulent strains of the fungus, which in layman terms means genetic engineering of the fungus to lower its virulence, making it weaker and easier for the tree to fight off infections. Both approaches are proving to be promising. Between the breeding programs bringing 1/16th of the gene pool from Chinese chestnut into the American chestnut gene pool at the American Chestnut Foundation and the RNA virus research at the University of Maryland which allows the virus attacking the fungus to spread more rapidly, there is a very strong possibility that we will once again see the majestic trees in the Appalachian forests.

In 2006 the oldest known stand of American chestnut was discovered in Pine Mountain near Warm Springs, Ga. The stand consisted of six forty-foot tall trees able to produce flowers and nuts. Pollen from this single surviving stand is one of the keys to unlocking the mystery. Scientists are hopeful that these trees will make it possible to regrow the American chestnut. In fact the foundation is so sure it is going to work they are selling genetically engineered seedlings of the American chestnut on their website during the optimal planting season beginning March 19, 2024, to foundation members at a rate of $90 per ten tree bundle. If you are interesting in saving a legacy you can learn more about their programs at

Until next week, stay safe and learn something new.

Scott Hamilton is an Expert in Emerging Technologies at ATOS and can be reached with questions and comments via email to or through his website at

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