The black walnut tree (Juglans nigra) is a native American hardwood found throughout the eastern and central United States. Also known as American or eastern black walnut, these tall trees provide valuable, fine-grained wood as well as tasty nuts and other byproducts from the shells and bark. In landscapes, black walnut trees offer shade and colorful yellow leaves in the fall, the University of Minnesota Extension service notes.
Black walnut trees prefer well-drained, moist and fertile soil. Mature trees can reach 100 feet tall, according to the Virginia Tech Department of Forest Resources and Environmental Conservation. The trees have straight trunks and narrow crowns. Black walnut bark is brown and marked with ridges, furrows and diamond patterns. The pinnate (feather-shaped) leaves alternate on either side of the leaf stem and measure 3 to 3 1/2 inches long. In the spring, black walnuts produce male and female flowers. The male flowers are catkins and the female flowers take the form of short, yellow-green spikes.
The walnut husk develops first, followed by the shell and the seed. The nuts ripen in September or October and fall off the tree at the same time as the leaves. The edible nut meat lies inside an oval, furrowed shell covered with an outer husk. Don't expect your black walnut trees to produce good seed crops right away. The University of Minnesota Extension Service says that most seeds begin producing good crops when they reach about 30 years old; after that, expect good crops only twice in every five years.
Furniture and gunstock makers use black walnut because of its durability and beautiful grain pattern. Because of heavy logging, black walnut has become scarcer, according to the Virginia Tech Non-timber Forest Products Program. Today, most furniture makers use thinner veneer rather than solid black walnut. The edible nuts make good snacks or additions to baked goods or ice cream. The bark and husks have medicinal uses. Ground-up shells add grit to metal cleaning and polishing compounds and texture to paints and varnishes.
Black walnut trees are disease- and insect-resistant. Some insects to watch for include aphids, fall webworms, walnut caterpillars and walnut lace bugs, according to the University of Minnesota Extension Service. These insects target leaves, twigs and nuts. Protect your black walnut trees from extreme cold, since freezing can damage limbs and kill the trees, the service warns.