Castanea dentata Seeds | American Chestnut

Long toothed chestnut leaves and a spiny green bur on an American chestnut sprout — American Chestnut (*Castanea dentata*): Fagaceae, once dominant in the forests of eastern North America.

LATIN NAME: Castanea dentata

COMMON NAME: American Chestnut

Plant Profile

American chestnut is a tree defined by what happened to it. A century ago it was one of the commonest and most useful trees of the eastern forest, four billion of them from Maine to Mississippi, growing straight and fast to thirty metres and bearing a sweet nut that fed people, hogs and wildlife. The wood was light, straight and rot-resistant, and it went into telegraph poles, rails, furniture and shingles. Then chestnut blight arrived, a fungus from Asia, and within fifty years the species was reduced to stump sprouts that grow, flower and die back before they can set much seed. What remains is a shrubby relict, and a hundred years of breeding work that has not yet produced a tree that is both resistant and American. The leaves are long, lance-shaped and sharply toothed, and the burs are spiny.

Science & Biotechnology

The blight is caused by Cryphonectria parasitica, an ascomycete that enters through wounds in the bark and grows in the cambium, girdling the stem and killing everything above the infection. The root collar survives, so the tree resprouts indefinitely, which is why the species has not gone extinct but has been functionally removed from the canopy. The fungus is a wound parasite and spreads in rain splash and on bark beetles. Hypovirulence, infection by a virus that reduces fungal virulence, can allow healing in Europe but has been unreliable in North America because of the diversity of fungal strains. Breeding has used backcrossing with the resistant Chinese chestnut, C. mollissima, over six generations to recover the American form, and a transgenic line carrying a wheat oxalate oxidase gene has been developed and is under regulatory review. The nuts are recalcitrant and cannot be dried or stored dry.

Uses & Benefits

Historically the nuts were a staple: roasted, boiled, ground into flour, and used to fatten livestock, while the timber was one of the best in the eastern forest for posts, rails and split fencing because the heartwood resists decay. Today the species has no commercial use, because there are no merchantable trees. What it has is a restoration project: backcross and transgenic material is being planted in national forests and on reclaimed mine land, and the species is a test case for what restoration means when the original genetics are gone. The nuts are still gathered from surviving sprouts and from orchards of hybrid material, and they are sweet and thin-skinned. The leaves have a folk record as a cough remedy, and the bark was astringent, but neither matters beside the tree’s history.

Growing from Seed

Sow fresh nuts in autumn, immediately, because they are recalcitrant and die if dried; keep them damp and cool, never below freezing for long. Sow two centimetres deep in a loose, acid mix, and expect germination in spring after natural cold. Protect the seed from squirrels, which will find it first. The seedlings grow fast, thirty to sixty centimetres in the first year, and they need deep, well-drained, acid soil and full sun. Plant out at thirty to forty centimetres with a tree tube or cage, since deer and voles will otherwise take them. Expect blight to arrive within a decade in the eastern United States; the tree will resprout, and the point of planting is usually to test resistance rather than to grow timber.

Our Take

Plant it as a restoration subject rather than a crop, and expect blight. The nuts must never dry out, and the seedling needs a cage against deer and squirrels.

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