American Chestnut Trees: History, Growing, and Blight-Resistant Varieties

The American chestnut (Castanea dentata) was once one of the most ecologically and economically important trees in eastern North America. An estimated three to four billion trees dominated the forests from Maine to Georgia and west to the Ohio Valley before chestnut blight arrived in the United States in the early 1900s. Within fifty years, the blight had eliminated American chestnut as a canopy species across its entire range.

The tree is not extinct. Root systems survived the blight, and American chestnuts still sprout from old roots across their historic range. However, the sprouts never grow large enough to reproduce before the blight kills them back to the root crown. The trees persist as root systems with no ability to mature.

Chestnut Blight

Chestnut blight is caused by the fungus Cryphonectria parasitica, introduced to North America from Asia on imported Japanese and Chinese chestnut planting stock around 1904. The fungus enters through bark wounds, kills the cambium in a spreading canker, and girdles branches and stems. The root system is resistant to the pathogen and survives indefinitely, but any aboveground growth is killed before it reaches reproductive maturity.

Asian chestnut species (Castanea mollissima, Castanea crenata) co-evolved with the blight fungus and are largely resistant to it, making them viable landscape and productive trees throughout the historic American chestnut range.

Blight-Resistant Varieties Available Today

Two sources of blight-resistant chestnut trees are currently available to homeowners.

Chinese-American hybrids. Several breeders, including the American Chestnut Foundation (ACF), have developed backcross hybrid trees that combine Chinese chestnut blight resistance with American chestnut growth habit and nut quality. These trees are available through specialty nurseries and the ACF. They are productive nut trees with good resistance to blight, though not fully immune.

Chinese chestnut (Castanea mollissima). Fully blight-resistant and widely available. Chinese chestnut matures at 40 to 60 feet, requires two trees for pollination, and produces large, sweet nuts. It is the most practical productive chestnut option for homeowners today.

Dunstan chestnut. A Chinese-American hybrid developed by Robert Dunstan in the 1950s that is widely planted across the southern United States. Blight-resistant, productive at a younger age than pure species, and tolerant of a broad range of soil conditions.

Growing Conditions

Chestnuts require well-drained, slightly acidic soil with a pH of 4.5 to 6.5. They are intolerant of waterlogged conditions and high-pH alkaline soils. Full sun is required for good nut production.

Plant at least two compatible varieties or seedlings for cross-pollination. A single chestnut tree produces little or no harvestable crop.

Chestnuts are hardy from USDA zones 4 to 8 depending on variety. Chinese chestnut is reliable from zones 4 to 9.

Harvesting

Chestnuts ripen in late September through October. They fall naturally from the burr when ripe and are collected from the ground. Do not attempt to force burrs open: the spines are extremely sharp and ripe nuts fall readily. Collect daily during harvest season as ripe chestnuts deteriorate quickly on the ground.