Smithsonian, September 2004
Wielding cutting-edge science and lots of patience. James Hill Craddock hopes to restore the ravaged American chestnut tree to its former glory
James Hill Craddock calls himself a chestnut breeder, but a truer description would be a chestnut evangelist. For the better part of his 44 years he has been preaching the virtue of the genus Castanea. "I think the world would be a better place with more chestnuts," he says. His particular concern is the American chestnut. Once known as the redwood of the East, the tree ruled forests from Georgia to Maine until it was devastated by chestnut blight in the first half of the 20th century. By 1950, the fungus had killed some four billion American chestnut trees—"the greatest ecological disaster in North America since the ice age," Craddock says.
Today, the towering American chestnut of old is very rare, and hardly an acre of its natural habitat is blight free. Yet Craddock, a biologist at the University of Tennessee at Chattanooga (UTC), persists in his optimistic mission of restoring the vanquished tree. At several experimental orchards outside Chattanooga, he is breeding scores of chestnuts in an effort to develop blight-resistant hybrids that could be planted in forests, helping reestablish what was once, he says, "the dominant tree in the canopy."
Craddock (his friends call him Hill) is well equipped for such a monumental undertaking. "I couldn't care less about chestnuts personally, but when I'm with Hill, he even gets me excited," says Charles Nelson, head of the UTC biology department. To win people over to his cause, Craddock has been known to serve up bowls of chestnut soup, heavy on the cream. "There's no one who doesn't like it," he claims. He planted his first chestnut tree when he was 15, and now, some 30 years later, is the recipient of an academic stipend devoted exclusively to the study and restoration of the American chestnut.
The tree once played a critical role in American life in the Eastern United States. The nuts that rained down each fall fed nearly all the inhabitants of the forest. The trees grew fast and tall and straight, reaching more than 100 feet high and as much as 9 feet in diameter in 75 to 100 years. The wood resisted rot and warping, making it a favorite for fencing, utility poles and furniture. People built homes from chestnut logs, buried their dead in chestnut coffins and fattened their hogs with the tree's nuts. In Appalachia, the blight dealt a blow as crippling as the Great Depression.
The disease was first observed in 1904 at the Bronx Zoo, and scientists soon determined that it was caused by a fungus. The "miserable stowaway," as one observer called it, had arrived in America on chestnut trees from Asia. In its native habitat, the fungus, Cryphonectria parasitica, is relatively benign. Asian chestnuts can shrug off an infection, but the American chestnuts quickly succumbed. The fungus, whose spores infiltrate tiny cracks in a tree's bark, can kill a healthy tree in a year.
And the blight moved with heartbreaking speed—carried by the wind, animals, insects and humans. Despite efforts to stop the pandemic, "it spread about 30 miles a year in concentric circles from New York City," says Craddock. By 1930 many of the chestnut trees in the forest canopy were dead or reduced to mere shrubs as far south as North Carolina and west to Ohio. The chestnut trees we see today outside forests are mainly European or Asian species, smaller and less majestic than their American kin. A few mature American chestnuts survive, but they are ravaged by cankers. There are also rare cases of isolated trees that have escaped the blight. And though the forests are full of chestnut saplings sprouting off the root systems of blight-infested trees, their growth is stunted. For decades it was thought that the stately American chestnut was lost to the past. But thanks to Craddock and others, it now may have a future.
Craddock's love affair with chestnuts began when he was growing up, near Woods Hole, Massachusetts. His father was a marine biologist and his mother, an emergency room nurse. He'd gardened since he was old enough to hold a trowel, and in his teens he became interested in sustainable agriculture. At 17 he read Tree Crops: A Permanent Agriculture, by J. Russell Smith, which described how Corsicans had raised chestnuts for food, lumber and forage for centuries without damaging the soil—in fact, they improved it. "It made a huge impression," Craddock recalls.
While attending the University of Indiana, where he studied art and biology, Craddock rode his bike all over Bloomington, collecting nuts from Chinese chestnut trees. He planted them in soil-filled milk cartons, then sold the seedlings at a local farmers' market. "I told everyone I met that they should plant chestnuts," he recalls. At Oregon State University, he earned a master's degree in horticulture.
Then, in 1987, he moved to Italy to be with Paola Zannini, an Italian botanist he'd met at Oregon State and would later marry. Craddock was thrilled to find himself in a place where chestnuts had been cultivated for thousands of years. He spotted his first chestnut tree during a drive through the Alpine countryside. A man was raking nuts under the tree's spreading branches. "I said to Paola, ‘Go and ask the man what kind of chestnuts they are.' Paola looked me in the eye and said, ‘First you learn Italian. Then you go ask the guy what kind of nuts they are.'" Craddock did as he was told and also earned a doctorate in pomology, the science of growing fruit, at the University of Turin. It was in Italy, he says, that he "realized someone would pay me to think about chestnuts."
The someone turned out to be Chattanooga philanthropist William Raoul, who met Craddock in 1995. Unbeknown to Craddock, Raoul had persuaded donors to help fund a UTC position dedicated, in part, to chestnut tree restoration. Craddock was asked to fill the job. At last, he had a pulpit for his chestnut gospel.
On a morning in early spring, Craddock steers a clanking maroon van south of Chattanooga toward Bendabout Farm, where he oversees three of his five experimental chestnut orchards. The chestnuts will soon be coming into bloom, giving him just a few weeks to do the matchmaking for a new generation. He seems slightly frazzled. "Chestnut breeding time," he admits, "is a time of great anxiety."
Craddock follows breeding procedures championed by corn geneticist Charles Burnham, who helped found the American Chestnut Foundation (TACF) in the early 1980s. Since that time, TACF has led the effort to breed blight-resistant hybrids at its experimental farm in Virginia. In the technique, known as backcrossing, successive generations of Asian-American hybrids are crossed with pure American trees. The idea, Craddock says, is first to transfer blight-resistance characteristics to the American species, then phase out all other Asian traits (the Asian trees, shorter and less hardy, are not well adapted to U.S. forests) by subsequent crosses with American chestnuts.
Scientists predict it will take at least five generations of crosses to produce a highly resistant tree. Even so, the odds are daunting: for every hundred trees produced, only a handful acquire resistance. "If you were a professional gambler," says Craddock, "you'd never bet on the American chestnut tree." Still, TACF's efforts appear to be paying off: the program expects to have its first blight-resistant nuts ready to test in forests by 2007 or 2008. But TACF's trees can't restock the entire Eastern United States, nor should they. A resistant hybrid that flourishes in Virginia could falter in Maine or Georgia, which is why TACF wants to develop local chapters that can draw on an area's native stock to breed blight-resistant trees. Craddock and his helpers, for instance, scoured Tennessee for remaining American chestnuts with which to create his first locally adapted hybrid generation.
He gestures proudly to a row of 15-foot-high saplings, their saw-tooth-edged leaves fluttering in the breeze. They are the first Tennessee hybrids that he bred, planted seven years ago. Each will soon be challenged with a shot of blight fungus, and those few that show some resistance will be selected for breeding the next generation. "Unfortunately, you've got to kill some of them," he explains, wagging the slim branch of one tree. "That's sad because they're my babies. But if we don't do it, we won't be able to make progress in the breeding program."
Craddock, like other chestnut researchers, is exploring another anti-blight strategy—using a virus to cripple the fungus. The virus, whose effects were first described by a French researcher in 1965, blunts the fungus' virulence, thereby giving the infected trees a fighting chance. U.S. researchers have been testing the virus since the early 1970s and have found that while the virus may save individual trees, the method isn't potent enough to protect a whole forest. Craddock and others suspect that the trees most likely to benefit from this method already have some ability to fight the blight. If so, chestnut restorationists may be able to use partially resistant trees coupled with virus control to outwit it.
It's one thing, of course, for chestnuts to thrive in an orchard and quite another for them to flourish in a forest. "From the plant's point of view, the forest is an extremely harsh environment," says Craddock. "Trees are competing for nutrients and light. And you've got the constant pressure of predation. There are insects and mollusks, mammals and fungi—and they're all trying to eat you. I don't think we can expect to plant seeds all over the mountains and come back in 50 years and find a chestnut forest." Still, Craddock is confident that chestnut forests will return. Not in his lifetime, but maybe in his grandchildren's. "If you really like chestnuts," he says, "you've got to be an optimist."