GARDENING : Want to Stand Under a Spreading Chestnut Tree? Try a Hybrid

Of all the species of chestnuts, none is finer than the American chestnut.

This majestic tree known as the Castanea dentata once towered to 100 feet high in America’s virgin forests and yielded a wood that was used in musical instruments, molding, fence posts, barrel staves, even telephone poles. The nuts of the American chestnut are deliciously sweet and flavorful.

But the sturdy chestnut had its weakness--chestnut blight. The disease, accidentally introduced from the Orient, was first noted at New York’s Bronx Zoo in 1904. It spread 25 to 50 miles a year and within 50 years had left 7 million acres of Appalachian forests with dead or dying chestnut trees.

The American chestnut is not gone, though. The tops, but not the roots, are susceptible to blight, so new sprouts continue to grow from the roots as older trunks are killed back to the ground.

Appalachian woods still contain whole groves that are spindly reminders of once-great chestnut forests. The sprouts, which succumb to blight only as they age, provide continual sustenance to the fungus that causes chestnut blight.

No need to write off the chestnut as a lingering, dying tree. Looking across the Pacific to Asia, home of the blight fungus, we find two blight-resistant chestnut species: the Japanese Chestnut (C. crenata) and the Chinese chestnut (C. mollisima).

Unfortunately, Japanese chestnut is an imp of a tree, often no more than a shrub, and its nuts, though enormous, are mediocre in quality.

The Chinese chestnut offers more hope to chestnut lovers. This tree lacks the grandeur of the American chestnut but does grow larger than any other chestnut commonly used for nut production. The trees bear at a young age, and the beautiful mahogany-colored husks yield delicious nut meats.

The chestnuts you see in food markets are European chestnuts (C. sativa), a species almost as susceptible to the blight as our native species. The nuts themselves vary in quality, from astringent to insipid to moderately sweet.

The American chestnut and the Chinese chestnut could be hybridized to produce a tree almost as majestic as the American chestnut, yet resistant to chestnut blight.

The Chinese species could infuse the hybrid with larger, more attractive nuts than the pure American species. Chinese and American chestnuts have, in fact, been hybridized, and hybrid trees are available from nurseries.

But some nostalgic folks still long for the purebred American chestnut.

Bringing back the American chestnut is one of the goals of the American Chestnut Foundation, and a number of avenues are being explored in pursuit of this goal.

For example, researchers have found that the fungus that causes chestnut blight is susceptible to a viral disease. Chestnut trees can live happily with a little blight if the blight fungi are virus-infected.

Natural spread of the virus has been effective in arresting the spread of blight in Europe, but the technique has met with only partial success under American conditions. Researchers also are using the new technique of genetic engineering to attempt to incorporate genes for blight resistance directly into American chestnuts.

There is also the possibility that an American chestnut tree with natural resistance to blight towers in solitude in some forest today, awaiting discovery. Chestnut lovers keep their eyes open to find such trees.

Through the combined research of plant breeders and plant disease experts as well as the observant eyes of everyday people, the American chestnut may one day return as a majestic tree for our back yards, streets and forests.

For the present, consider planting Chinese-American or Chinese chestnut trees. Choose a good soil and a sunny site sheltered from spring frosts to reinforce the trees’ natural resistance to blight.

You need two seedlings or two different varieties of grafted trees in order to get nuts. Expect to roast your first batch of nuts within five years.