The American chestnut (Castanea dentata) was once a major part of America’s forests in the eastern states. Besides its beauty, size, speed of growth and longevity, its rot-resistant and straight-grained timber was highly valued for use in furniture, fencing, and for building materials. The nuts of the American chestnut were used as feedstock for cattle and were a traditional food during winter holidays.
Unfortunately, during the past 100 years or so, chestnut blight (Cryphonectria parasitica) and ink rot disease (Phytophthora cinnamomi) have caused the American chestnut to be designated as ‘functionally extinct’ – meaning that though the species still technically survives, it cannot reproduce.
The American chestnut is not completely defenseless against blights, as the blight cannot kill the underground root system due to the pathogen being unable to compete with soil microorganisms. This allows the roots to remain viable and send up shoots to create a “chestnut shrub.” Studies have estimated a population of 430 million wild American chestnuts still growing. However, the portion of the tree above-ground will succumb to the blight within about five to 10 years.
Hybrid chestnut trees
Efforts are underway to bring the species back to its former glory. At least 50 strains of the fungus have been identified, and Chinese chestnut trees have been found to be resistant to all of them. Hybrid chestnut trees – which are fifteen-sixteenths American chestnut and one-sixteenth Chinese chestnut (Castanea mollissima) – were bred by The American Chestnut Foundation and have been successfully planted in many test locations.
Genetic engineering is also being examined, with biotechnologists using a gene from wheat called oxalate oxidase (OxO). The OxO enzyme breaks down oxalic acid, one of the primary factors in how the blight fungus attacks chestnut trees. More than 100 varieties are gradually being introduced into test gardens across the country.
So, can you incorporate this magnificent tree into your landscaping?
The fungal blights are mostly found in the eastern U.S., but there is always the small possibility of an attack on trees in any region. Using the hybrid varieties available will greatly increase your chances of success. According to the USDA, zones 2,3,4 and 5 in Minnesota are among the most favorable for its growth.
Choose your location
Chestnuts are large and fast-growing, so open fields may be your best choice for location. They are a hardy species, but will do best in well-drained, acidic soil on a sheltered, north-facing slope with full sun. Some growers suggest looking at the trees on the surrounding property – if the land supports large oak and hickory trees naturally, it should also be suitable for chestnuts. Be sure to protect your seedlings with wire cages or tubing, as the leaves and soft bark are tempting food sources for wildlife.
If you hope to have chestnuts in future, keep in mind that you will need at least 2 chestnuts to get nut production and the trees must reach maturity before production. In USDA zone 5, for example, they may bear between 5 and 7 years of age. At full maturity (in 15-20 years), each tree can produce as much as 50-100 lbs of nuts.
The new hybrid American chestnut trees
The new hybrid American chestnut trees have a number of advantages: they are a valuable food source; they do not require herbicide or pesticides to thrive; and their enhanced disease resistance and ease of growth make them more affordable than their native chestnut counterparts. Each tree planted will greatly help in the recovery of the species, as – in the wild – oak trees have become the predominant tree species in many native forests. The recent advances in knowledge in breeding, biotechnology, and forestry can bring the American Chestnut tree back from the brink of extinction to its natural place in our world!