The American chestnut was once a forest giant, but a fungus brought it down.

Gardening · Published 3 October 2026 Swipe more like this →

In short: Before the 20th century, the American chestnut was a dominant, fast-growing titan of eastern North American forests. Then, an accidental fungal introduction triggered a catastrophe, killing billions of trees. Today, scientists are racing to resurrect this lost icon through genetic engineering and cross-breeding, hoping to restore a vanished ecosystem.

The American chestnut, Castanea dentata, was once a cornerstone of the eastern United States landscape. These fast-growing hardwoods, which could reach heights of 30 meters, provided essential mast for wildlife and indigenous populations while serving as a primary source of lumber. Their sudden decline began in the early 20th century following the accidental introduction of the fungus Cryphonectria parasitica, which originated from Asian chestnut species. This pathogen, known as chestnut blight, spread with devastating efficiency, effectively removing the species from its native range.

Estimates suggest that between three and four billion trees succumbed to the blight during the first half of the 20th century. While the species was virtually eliminated as a canopy-forming tree, it did not vanish entirely. Living root systems continue to produce stump sprouts, though these saplings are typically girdled and killed by the fungus before they can reach maturity. The loss of the chestnut significantly altered forest structures, leading to the expansion of oak and hickory species in areas where the chestnut once thrived.

Modern restoration efforts focus on developing blight-resistant cultivars. One prominent approach involves the Darling 58 cultivar, developed by researchers at the SUNY College of Environmental Science and Forestry. By inserting an oxalate oxidase gene from wheat into the American chestnut genome, scientists aim to help the tree degrade the oxalic acid produced by the fungus, thereby protecting the vascular cambium. If approved for release, these would be the first genetically modified forest trees introduced into the wild in the United States. Other researchers are pursuing traditional cross-breeding methods, attempting to combine the blight resistance of Asian species with the genetic profile of the American chestnut.

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