Walnut, Black

The black walnut is a large deciduous tree attaining heights of 98–130 feet. Under forest competition, it develops a tall, clear bole; the open-grown form has a short bole and broad crown. While its primary native region is the Midwest and east-central United States, the black walnut was introduced into Europe in 1629. It is cultivated there and in North America as a forest tree for its high-quality wood. Where the range of J. nigra overlaps that of the Texas black walnut J. microcarpa, the two species sometimes interbreed, producing populations with characteristics intermediate between the two species.

The LEAVES are alternate, pinnately compound, 12 to 24 inches long with 10 to 24 leaflets (poorly formed or missing terminal leaflet), leaflets are ovate-lanceolate, finely serrate, and 3 to 3 1/2 inches long, rachis is stout and somewhat pubescent; yellow-green to green above, slightly paler below.

The male FLOWERS are on drooping catkins 2 1/2 to 5 1/2 inches long. The female flowers on short spikes near twig end, in clusters of two to five, yellow-green in color, appearing in late spring.

The FRUIT (nut) ripens during the autumn with a brownish-green, semi-fleshy husk and a brown, corrugated nut that contains sweet, oily meat (edible). The whole fruit, including the husk, falls in October; the SEED is relatively small (compared to the husk) and very hard. The tree tends to crop more heavily in alternate years. Fruiting may begin when the tree is 4–6 years old, however large crops take 20 years. Total lifespan of J. nigra is about 130 years.

The TWIGS are stout, light brown, with a buff-colored chambered pith; buds are tan, and large with a few pubescent scales; leaf scars are 3-lobed, resembling a “monkey face”.

The BARK is brown on the surface, darker brown when cut, ridged and furrowed with a rough diamond pattern.

WILDLIFE: Squirrels and other sharp-toothed rodents feed on the nuts throughout the late fall to winter months. They bury the whole nut (hoard) for later recovery. Most unrecovered nuts grow into new trees.

The WOOD is used to make furniture, flooring, and rifle stocks, and oil is pressed from the seeds. Nuts are harvested by hand from wild trees. About 65% of the annual wild harvest comes from the U.S. state of Missouri, and the largest processing plant is operated by Hammons Products in Stockton, Missouri. The black walnut nutmeats are used as an ingredient in food, while the hard black walnut shell is used commercially in abrasive cleaning, cosmetics, and oil well drilling and water filtration.