Spreading and Spreading the Chestnut Tree

By Tom Horton

(June 2, 2010) Their progress on restoring the Bay has faltered, but Pennsylvania, Maryland and Virginia are on the verge of a cooperative success in bringing back one of the world's great forests.

In the last year, modest but historic plantings of a disease resistant American chestnut have begun on national forest lands in Virginia and on a private tract in Westmoreland County, Pa. The little trees, also the basis for an ambitious science curriculum in Carroll County, Md., schools, represent the sixth generation of a breeding program begun 25 years ago to counteract the chestnut blight.

Perhaps no 'perfect' tree ever existed, but the American chestnut came close. It grew straight and tall and fast, to a hundred feet high and several feet in diameter. Its easily-worked, rot resistant wood was sought for everything from pianos to railroad ties.

Billions of chestnuts grew from Maine to Georgia, Arkansas to Michigan, comprising an estimated quarter of the eastern hardwood forest. Their fruit, high in fiber, Vitamin C, protein and carbohydrates, and low in fat, was prized by wildlife from squirrels and turkey to black bears, and by human settlers, who derived nutrition and income from chestnuts.

Their profusion of creamy, June blooms was described by a writer as making the Appalachians "a sea with white combers plowing across its surface." This supported bees and other pollinators, and because chestnuts blossom late, their nut crop was never hit by late frosts that can diminish the mast of oaks, hickories and beeches. The Romans ranked chestnuts alongside the olive tree and grapevine as plants important to civilization.

That annual exuberance of the chestnut began to fade from the landscape around 1904, when a blight imported on Asian chestnuts began rampaging from Maine to Georgia. By the 1950's destruction was complete. Old chestnut stumps still send up shoots, but the blight, a virus spread by wind and birds, remains potent, felling them in a few to several years.

The small "Restoration" chestnuts now being deployed are 15/16ths native and a sixteenth blight resistant Chinese, virtually identical in form, growth rate and wood quality to the original American chestnut.

"It's probably not the best tree we can achieve, but it's good enough to start planting on a landscape scale," says Kim Steiner, director of Penn State University's arboretum.

The breeding has been done under the auspices of the private American Chestnut Foundation, founded in 1983, the same year the Chesapeake Bay restoration program began. At a farm in Meadowview, Va., and in complementary programs in Pennsylvania and other states, American chestnuts have been crossed with Chinese varieties; then the progeny are 'backcrossed' to native American trees.

It is a labor intensive process. The trees are hand pollinated, with female flowers bagged in plastic to keep out undesired pollen. Then the breeders wait for the offspring to grow, inoculate them with the chestnut blight and select as few as one of every 150 trees that show the best resistance and most native-like growth habit. Then they do it all over again, each time gaining resistance in trees successively closer to the original American.

In Maryland, the Carroll county school system has developed a unique STEM (science, technology, environment, math) curriculum around restoring the chestnut, involving some 18,000 students annually.

In 16 chestnut orchards, middle schoolers measure growth, calculate carbon storage and learn tree identification. Upper grades study forest ecology, perform DNA experiments and study genetics. AP statistics students analyze data from other experimental chestnut orchards across the east.

"It generates such excitement…. What's more American than a chance to restore this tree that was a cornerstone of the forest economy and ecology," says Brad Yohe, science supervisor for Carroll County schools.

Meantime, restoring chestnuts is progressing on two other fronts. University of Maryland virologist Donald Nuss has created a transgenic chestnut blight whose impact on native chestnuts is relatively mild.

The idea is that the transgenic blight, derived from naturally occurring weaker forms of the original blight, can act as a vaccine. It works in experiments, Nuss says, but so far the 'vaccine' hasn't spread on its own, the only way to effectively inoculate chestnuts at landscape scale.

In New York, researchers at the state university's Environmental Science and Forestry school in Syracuse are about a year away from sequencing the genes in the chestnut. Then they expect to produce a chestnut that is pure American except for a few genes from the Chinese that confer blight resistance.

Penn State's Steiner says all evidence is that the chestnut, if the blight is overcome, can take hold rapidly, outcompeting most other forest trees.

University of Arkansas scientist Fred Paillet, wonders whether it's possible that the chestnut will someday be seen as virtually "invasive….a problem I would gladly live with."

Tom Horton covered the Bay for 33 years for The Sun in Baltimore, and is author of six books about the Chesapeake. He is a freelance writer, splitting his time between Baltimore and Maryland’s Eastern Shore.

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