We’ve all heard the familiar holiday tune that begins “chestnuts roasting on an open fire,” but in most parts of the United States, American Chestnut trees are not a familiar sight, said a University of Illinois Extension unit horticulture educator.
“The American Chestnut, Castanea dentata, used to be one of the most important forest trees in the eastern U.S. and southeastern Canada,” Jennifer Schultz Nelson said. “It was also one of the largest, growing up to 150 feet tall with a trunk up to 10 feet in diameter.
“The wood from American Chestnut trees was at one time a prized commodity. It has a straight grain, is easy to split and is very strong wood. The wood is highly resistant to decay, making it a good choice to use in outdoor projects,” she added.
As the song tells us, the nuts were also valued as food and are especially good roasted. Some cooks also use them raw or ground into flour. As American Chestnuts have become harder to find, stores more often sell the commonly available Sweet Chestnut instead.
American Chestnuts were also an important food source for both wild animals and livestock. The stately trees were anchors in the landscape and a source of valuable shelter for birds and other wildlife.
“But in the early 1900s, the beautiful American Chestnut began to disappear from forests in the U.S. and Canada,” Nelson said. “The culprit is a familiar theme heard in other tragic demises of plant species: foreign disease.
“Asian Chestnut trees (Castanea crenata or C. mollissima) were imported into the U.S. in the late 1800s as specialty trees. Unfortunately, there was a hitchhiker on these trees: the fungus that causes chestnut blight, Cryphonectria parasitica.”
The fungus infects a tree through wounds such as cracks in the bark. The blight disease develops and eventually girdles and kills the tree. Scientists hypothesize that the fungus spreads with the help of an insect or other carrier, by airborne spores, or is washed from tree to tree in the rain.
The Asian Chestnut species have developed some resistance or tolerance to this fungus, but the American Chestnut had no previous exposure to the fungus before its arrival in the U.S. in the early 1900s, so it was completely vulnerable. The first trees to show symptoms were noted in the Bronx Zoo in 1904.
“Experts estimate that 3.5 billion to 4 billion trees were lost to chestnut blight across the eastern U.S. and Canada in less than 50 years,” Nelson said. “By some unknown mechanism, rare stands of American Chestnut that had been planted outside of their native range were spared the death sentence of chestnut blight.”
Today, researchers are very interested in these rare stands of trees, she added. They are the only surviving relics that can provide clues about the American Chestnut’s role in forest ecosystems and perhaps provide insight as to why these stands did not succumb to chestnut blight.
“Other research efforts involve breeding the American Chestnut with their Asian cousins that have resistance to chestnut blight,” Nelson said. “There may be opportunities in the future for landowners to acquire these blight-resistant trees for the landscape. Asian Chestnut species are still available and may be a good choice for landscapes with room for these large trees.”