The black walnut, also known as the American walnut, is a deciduous tree native to the central and eastern parts of the United States. The black walnut tree was introduced to Europe in the early 17th century, and is currently cultivated in North America and Europe. The term may also be used to describe the fruit of the tree, which drops to the ground in the late fall. These trees can reach heights of up to 150 feet (45.7 meters), thriving in small groves in mixed forest lands.
Black walnut bark is deeply furrowed, dark gray to black in color, and has a rough diamond pattern. The compound leaves grow alternately, and can reach up to 24 inches (61 centimeters), each with 10 to 24 smaller leaflets growing up to 3.5 inches (8.9 centimeters) in length. Black walnut trees flower in the late spring, with males producing single-stemmed catkins, and females producing short flower spikes near branch ends.
The walnut fruits, also known as simply black walnuts, are round and hard with a thick green husk. A hard, furrowed nut is found inside the husk, containing an edible nut meat, which is harvested commercially for food. Black walnuts are used to make black walnut ice cream and the popular flavoring, black walnut extract.
Black walnut wood has been heavily harvested to make fine furniture, gunstocks and flooring. Today, the wood is used primarily to make veneer due to a decrease in availability. The husk of the black walnut is used to make dye and wood stain. Early American settlers used the dye to color hair, but it is used in modern times for basket-making and other wood craft projects.
Native Americans used the bark, leaves and fruit of the tree for medicinal purposes, and some traditional herbalists still employ these remedies for the treatment of various ailments. The inner bark of the tree is made into a laxative tea, or chewed to reduce toothache pain. The husk of the black walnut is made into a poultice for skin inflammation, or applied to treat ringworm. A black walnut infusion, made of the leaves and nuts of the tree, is used to treat stomach cramps and colic.
The leaves, twigs and fruits of this walnut contain juglone, a chemical which inhibits the growth of other plants near the tree. This is nature's way of ensuring all the beneficial nutrients in the soil are available to the black walnut. However, some plants can withstand the chemical, including goldenrod and fescue grass, making it difficult for the tree to survive. These invading plants may be removed with herbicide if necessary, to keep the tree healthy and thriving.