The black walnut tree (Juglans nigra) grows from southern areas of New England south to Georgia and west to Texas in the South and to Minnesota in the North. Black walnut trees are what the Ohio Department of Natural Resources website calls a pioneer invader species, growing in open fields or in woods where people have cut down trees. The tree has many points of identification, including one that focuses on the ground beneath the tree.
The average black walnut tree grows to be about 50 to 75 feet tall. The spreading top of the black walnut is often as wide as the specimen's height. The trunk's diameter can reach to 3 feet on a black walnut. The compound leaves can be up to 2 feet in length and the fruit is as wide as 2.5 inches.
The leaves of a black walnut are pinnately compound, composed of two separate rows of leaflets growing out of a central stalk. A black walnut can have as many as 23 individual leaflets, each as long as 5 inches, arranged on a stalk making up just one leaf. The leaflets are dark green, shaped like a lance and have fine serrations along their edges. They will rain down from the tree in the fall after they turn yellow, collecting under the walnut tree.
A rich brownish dye will stain your hands if you attempt to handle the fruit of the black walnut tree. The nut has a fleshy covering inside a green husk. As the nut ripens, the husks turn yellow-brown and emit the substances that will get on your clothes and hands if you pick them up. Freed from its husk, the kernel has a protective shell around it made up of two halves seemingly fused together.
Younger black walnut trees have flaky dark bark that will develop deep furrows and discernable ridges as the tree gets older. The bark takes on a black shade from which the tree gets its name. Other recognizable features of a black walnut include its flowers, which are both male and female. The male flowers resemble green scaly cones and hang from the branches. The female flowers are in clusters at the tips of what seem like spikes.
Looking under a black walnut tree, you may often notice that the ground in the immediate vicinity of the trunk is bare. This is due to a substance that the roots produce called juglone. This chemical can stop many types of plants from growing under the tree, leaving a bare patch beneath the specimen even in a woodland setting. It seeps into the soil around the tree and adversely affects plant growth.