The American chestnut (Castanea dentata) once dominated the forests of the eastern United States, earning the nickname “Redwood of the East.” This tree was a foundational species, forming up to a quarter of the hardwood canopy across its native range from Maine to Mississippi. Its straight-grained, rot-resistant wood was prized for everything from fence posts and barn beams to furniture. Beyond its lumber value, the chestnut produced an annual, reliable crop of nuts that sustained wildlife and provided a significant food and cash crop for rural communities. This historical importance explains the widespread interest in acquiring the tree today, nearly a century after its disappearance as a mature forest giant.
The American Chestnut Blight and Its Legacy
The near-total loss of the American chestnut was caused by an introduced fungal pathogen, Cryphonectria parasitica, which arrived in the United States around 1904. This fungus, known as chestnut blight, was likely transported on nursery stock imported from Asia. Unlike Asian chestnut species, which co-evolved with the fungus and developed resistance, the American chestnut had no natural defense.
The fungus enters through bark wounds and rapidly grows, creating sunken or swollen cankers that girdle the trunk or branches. This process interrupts the tree’s ability to transport nutrients, leading to the death of the tissue above the canker. The blight spread across the chestnut’s range, killing an estimated three to four billion trees within a few decades. While the fungus does not kill the root system, it reduces the tree to a functional shrub, as new sprouts are continually infected and killed before reaching reproductive maturity.
Availability: Purchasing Blight-Resistant Varieties
The pure, wild-type American chestnut tree is generally not available for purchase because it remains immediately susceptible to the blight fungus. The modern answer lies in blight-resistant varieties developed through decades of scientific breeding and genetic engineering. The most common varieties sold are products of the backcross breeding program, which aims to combine the timber-form and genetics of the American chestnut with the disease resistance of the Chinese chestnut.
This traditional breeding method involves crossing an American chestnut with a blight-resistant Chinese chestnut, then repeatedly crossing the resulting hybrids back to American chestnuts for multiple generations. The goal is a tree that retains nearly 94% of the American chestnut’s genome, while having intermediate resistance to the blight. These hybrid trees offer a moderate level of tolerance, which allows them to grow larger and reproduce before succumbing to the disease.
Transgenic Trees
Another approach involves the development of transgenic trees, such as the Darling 58, which was engineered to contain an oxalate oxidase gene from wheat. This gene helps the tree neutralize the oxalic acid produced by the fungus, resulting in blight tolerance. However, the widespread commercial availability of these transgenic trees is still pending federal regulatory approval from agencies like the USDA and EPA. Furthermore, The American Chestnut Foundation has withdrawn support for the Darling 58/54 line due to performance concerns and confusion over the genetic material used in testing.
Sourcing and Planting Considerations
When seeking to buy a blight-resistant chestnut, the most reliable sources are specialized conservation nurseries and organizations like The American Chestnut Foundation (TACF). The trees offered by TACF and its partners are typically the hybrid backcrosses, which provide the best current option for combining American characteristics with intermediate resistance. Purchasing from these sources often supports the ongoing research and restoration efforts.
Successful establishment of these trees requires attention to specific environmental factors. Chestnut trees need a minimum of eight hours of direct sunlight daily to thrive and produce nuts. They require well-drained, acidic soil, ideally with a sandy or loamy texture and a pH between 4.5 and 7.0.
A key planting consideration for nut production is the need for cross-pollination, as chestnut trees are wind-pollinated and not typically self-fertile. It is strongly recommended to plant a minimum of three seedlings, spaced 30 to 40 feet apart, to ensure genetic diversity and successful nut set. Even with the intermediate resistance of hybrid trees, monitoring for blight symptoms remains important, and selecting a planting site that avoids heavy clay or poor drainage is essential for tree survival.