Female flowers are rounded and have conspicuous, red-fringed stigmas. The fruit is borne singly or in pairs and enclosed in a solid green husk which does not split open even after the nut is ripe. The nut itself is black with a very hard, thick, finely ridged shell, enclosing a rich, oily kernel which is edible and highly nutritious. This tree produces the black walnut nuts of commerce, but the fruit is considered a liability in an urban site. Walnut trees are easily propagated from the nuts.
Seedlings grow rapidly on good soils.
The heartwood is of superior quality and value. Black walnut is the most valuable timber species in Ohio. It is heavy, hard, strong, and of a rich, chocolate brown color. Freedom from warping and checking, acceptance of a high polish, and durability make it highly prized for a great variety of uses, including furniture and cabinet work, gun stocks, and airplane propellers. Small trees are mostly sapwood, which is light-colored and not durable.