Volunteers aim to revive American chestnut tree

Associated PressDecember 23, 2012 

WEAVERVILLE, N.C. -- Jim Hurst has doted on his trees, arranged in three “families” on a bluff high above the rushing French Broad River.

He installed a drip irrigation system to help rejuvenate this former hayfield’s powdery, depleted soil. To protect against browsing deer, he girded the delicate sprouts in plastic sleeving and wire mesh. In the four years since planting the fuzzy, deep-brown nuts, he nursed the seedlings -- through back-to-back droughts, a killing frost, even an infestation of 17-year locust -- applying herbicides and mowing between the rows to knock down anything that might compete.

Then, on a hot day this past June, Hurst moved methodically along the steep hillside, a petri dish in his left hand, and infected the young saplings with the fungus that will almost certainly kill them.

It wasn’t malice, but science -- and hope -- that led him to take such an action against these special trees.

“My mother’s family never stopped grieving for the (American) chestnuts,” the 51-year-old software engineer and father of two said as a stiff breeze rustled through the 110 or so surviving trees, many already bearing angry, orange-black cankers around the inoculation sites.

“Her generation viewed chestnuts as paradise lost.”

Hurst hopes the trees on his hillside farm -- part of a vast experiment in forest plots where this “linchpin” species thrived before the onslaught of an imported parasite -- might hold the key to regaining that Eden.

The American chestnut once towered over everything else in the forest. It was called the “redwood of the East.” Dominating the landscape from Georgia to Maine, Castanea dentata provided the raw materials that fueled the young nation’s westward expansion, and inspired the words of Henry Wadsworth Longfellow and Henry David Thoreau.

Then, the blight struck. By the 1950s, this mightiest of trees was all but extinct -- “gone down like a slaughtered army,” in the words of naturalist Donald Culross Peattie.

Now, after 30 years of breeding and crossbreeding, The American Chestnut Foundation believes it has developed a potentially blight-resistant tree, dubbed hopefully, the “Restoration Chestnut 1.0.”

At a national summit in Asheville, N.C., in mid-October, the group’s board adopted a master plan for planting millions of trees in the 19 states of the chestnut’s original range.

This year, volunteers in state chapters established seed orchards that will soon begin producing regionally adapted nuts for transplanting into the wild. But as those who attended the recent summit heard, much hard work remains -- and much uncertainty.

The restoration tree is being introduced onto a physical and economic landscape that has long since learned to do without the once-indispensable American chestnut. Will it crowd out other trees and plants that we have come to value in the past century? How do you convince landowners and government agencies that it’s worth the money and effort?

And there are those who will question the wisdom of trying to bring back something that could not survive on its own or, worse yet, “engineering” a replacement that can. But Hurst and the others at the summit are confident there is no obstacle they can’t overcome in the effort to restore the East’s “cathedral forests.”

“I think that’s something worth fighting for,” he said. “To fix something that’s broken.”

***

In the spring of 1540, Spanish conquistador Hernando de Soto’s quest for silver and gold brought him to the Blue Ridge Mountains, in what is now western North Carolina. A survivor of the expedition would later record: “Where there be mountains, there be chestnuts.”

More than 400 years later, Peattie conjured that virgin landscape in full flower: “the great forest below waving with creamy white Chestnut blossoms in the crowns of the ancient trees, so that it looked like a sea with white combers plowing across its surface.”

With trunks measuring 10, 12, even 17 feet in diameter, the trees’ branches soared up to 120 feet above the forest floor.

Along the continent’s Appalachian spine, chestnuts covered some 200 million acres -- comprising fully a quarter and, in some places as much as two-thirds, of the upland forest. It is difficult to overstate the tree’s importance.

Settlers built cabins, rail fences and barns out of its light, strong, even-grained wood. They hunted deer, turkeys and squirrels made fat on its mast -- and themselves feasted on the sweet, starchy nuts.

Thoreau wrote lovingly of going “a-chestnutting” in the New England woods. In an 1857 journal entry contemplating the chestnut’s spiny bur, he rhapsodized on the wonderful care with which nature “has secluded and defended these nuts, as if they were her most precious fruits, while diamonds are left to take care of themselves.”

Tannins from the tree’s bark cured the leather for belts that powered machines that drove the Industrial Revolution. The chestnut’s naturally rot-resistant wood supplied most of the railroad ties and telegraph poles that knitted together the rapidly expanding United States.

“At last when the tree can no longer serve us in any other way,” forest economist P.L. Buttrick observed, “it forms the basic wood onto which oak and other woods are veneered to make our coffins.”

But by the time he wrote those words in 1915, a death knell had already sounded for the American chestnut.

It is unclear exactly when or how the blight arrived here, though most agree it came on chestnut trees imported from China or Japan. The fungus -- Cryphonectria parasitica -- was first identified in 1904 by employees of the New York Zoological Park and was soon detected in chestnuts as far south as Virginia.

Entering through wounds in the bark, the fungus threads its way through the straw-like vessels that carry water and nutrients from the ground to the tree’s crown. As the tree responds to plug these holes, the blight works its way around the trunk “until it is completely girdled,” William A. Murrill, the botanical garden’s assistant curator, wrote in 1906.

“The tree essentially commits suicide,” said geoscientist Frederick Paillet, an emeritus professor at the University of Arkansas who has studied chestnuts for nearly a half century.

Carried by insects and on the wind, the blight cut through the forests like an invisible scythe. By the mid-20th century, it had spread throughout the entire range -- killing an estimated 4 billion trees in one of the worst ecological calamities in U.S. history.

But the American chestnut has not disappeared altogether. Millions of seedlings still sprout each year from old stumps or long-buried nuts. Most reach just a few feet in height before the blight, which persists in the soil and on the bark of surrounding trees, ultimately finds and kills them.

Occasionally, someone will stumble across a tree that has managed to live long enough to flower. Such specimens are referred to as LSA’s -- “large surviving Americans.”

Last year, Traylor Renfro was clearing trails at his mountaintop retreat in Grassy Creek, near the Virginia border, when something pricked his finger. At first, he thought he’d been stung.

“And then when I looked at it, I realized that it was a bur,” he said.

He was aware of the blight, and so his prime suspect was one of the bushlike chinquapins scattered about. His search for more burs led him to a nearby tree, its long, feather-like leaves edged with teeth that resemble breaking ocean waves.

It was an American chestnut -- about 37 inches around and at least 50 feet tall.

Nearby, Renfro found several young chestnuts that had sprouted from a desiccated, diseased stump. Examining the larger tree with a ladder, he could see no signs of blight -- giving him hope that his tree had somehow developed a defense against the fungus.

***

Soon after the blight was discovered, the U.S. Department of Agriculture began trying to develop a hybrid that was resistant and would grow tall enough to produce marketable timber. Because Chinese and Japanese trees, unlike the American ones, had evolved along with the blight, the emphasis was on crossing native trees with the foreign ones.

“It didn’t matter whether it looked like an American chestnut,” said Kim Steiner, a professor of forest biology at Pennsylvania State University. The goal was simply “some sort of a timber tree.”

After decades and millions of dollars, the government gave up. To be honest, purists weren’t interested in what the government was after, Steiner said.

“We’re not talking about replacing American chestnut,” he said. “We’re talking about restoring American chestnut.”

Enter Charles Burnham.

In 1983, Burnham and several other plant scientists formed The American Chestnut Foundation -- built on his program of “backcross breeding.”

Burnham started out with a hybrid between an American and a Chinese chestnut, then backcrossed it with a “pure American.” The progeny of that pairing were then backcrossed to American chestnut a second time; the offspring from that coupling were then crossed a third time back to American stock.

Since an American chestnut parent always passes some of the blight-susceptible genes to its progeny, the backcross -- or B3 -- trees are then intercrossed among themselves so their progeny have a chance of inheriting resistant genes from both parents, said Fred Hebard, chief scientist at the organization’s main research farms near Abingdon, Va.

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