Black Walnut

Black walnut is propagated by seed sown in fall into moist, deep, well-drained soil rich in organic matter, since its long taproot makes transplanting difficult once established. It prefers full sun and tolerates partial shade but not full shade; seed can be prechilled for three to four months at 34–40°F to aid germination, and trees grown in dense stands compete for light, producing the tall, clear trunk favored for timber.

Siting: All parts of the tree, especially the buds, roots, and nut hulls, release the compound juglone, which inhibits nearby plants such as tomatoes, apples, blueberries, azaleas, and peonies, causing foliar yellowing, wilting, and eventual death, so it should be sited away from garden beds. The tree tolerates a wide range of soils from wet to dry and acidic to slightly alkaline, though growth slows markedly on drier, less fertile ground.

Black walnut is affected by a range of diseases including parasitic nematodes, mistletoe, fusarium canker, bacterial blight, white trunk rot, root rot, anthracnose, leaf spot, and shoot dieback, and in some areas it faces pressure from thousand cankers disease. Insect problems include aphids, fall webworm, walnut caterpillar, acorn weevil, and other foliage-chewing caterpillars.

The nut ripens inside a semi-fleshy husk that turns from yellow-green to black between October and November, and the husk stains skin and clothing while being difficult to separate from the hard, corrugated shell beneath it. Trees can begin bearing nuts as early as six years of age, though a substantial crop usually takes about twenty years, after which bearing typically continues yearly; squirrels gather and cache the nuts, aiding the tree's spread.

Culinary: The nuts are edible, though laborious to extract from husk and shell, and are valued for the distinctive flavor they lend to baked goods and candy-making.

Industrial: The heartwood is prized for furniture, cabinets, and veneer for its rich color, attractive grain, and resistance to warping, while crushed nutshell has been used in cleaning abrasives and explosives, and the husk has served as a source of dye.

Ornamental: The tree is planted as a shade tree, though its open crown, early leaf drop, and messy nuts make it a less favored choice than other species; it also supports wildlife by hosting the larvae of the hickory horndevil moth, banded hairstreak butterfly, and luna moth, and is grown in butterfly and nighttime gardens.

Traditional: Cherokee people brewed the bark into a tea used as a laxative and chewed it for toothaches, though the bark is noted as poisonous and requiring caution; the Comanche made a paste from the leaves and husk for ringworm, and several peoples including the Appalachian, Cherokee, Comanche, Iroquois, and Rappahannock used the tree to address athlete's foot and hemorrhoids and as an insecticide.