Juglans nigra is a deciduous tree species in the family Juglandaceae, commonly known as the eastern black walnut. It is native to eastern North America, particularly the central and eastern United States, where it grows in rich, well-drained soils along river valleys and forested regions. The genus name Juglans derives from Latin Jovis glans, meaning “nut of Jupiter,” while the species epithet nigra means “black,” referring to the dark bark and husk of the fruit. The tree has been valued historically by Indigenous peoples and later by European settlers for its nuts, wood, and dye-producing husks.

The tree can grow to considerable height with a broad canopy, producing compound leaves and round drupaceous fruits enclosed in thick green husks that darken as they mature. Inside the husk is a hard, ridged shell containing the edible kernel. Compared to the more widely cultivated English walnut (Juglans regia), black walnut has a stronger, more robust flavor and a harder shell that makes processing more labor-intensive. It is both harvested from wild trees and cultivated on a smaller commercial scale.

As a food source, Juglans nigra provides edible nuts that are used in baking, confections, ice cream, and savory dishes. The kernels have a distinctive, earthy, and slightly bitter flavor that is highly valued in regional American cuisines. The nuts can be eaten raw or roasted while the young green fruits can be incorporated into processed foods such as nocino and black walnut ketchup. In addition to culinary uses, the husks have historically been used to produce dark brown dyes and inks due to their high tannin content.

Nutritionally, black walnuts are rich in lipids, particularly unsaturated fatty acids such as linoleic acid and oleic acid, as well as protein, dietary fiber, vitamins (including vitamin E), and minerals such as magnesium and phosphorus. They also contain bioactive compounds including phenolic acids, flavonoids, and tannins, which contribute antioxidant properties. Juglone (5-hydroxy-1,4-naphthoquinone), a notable compound produced by the tree, has allelopathic effects that inhibit the growth of surrounding plants and has been studied for antimicrobial and cytotoxic properties.