The most common identifying characteristics of a black walnut tree are found in its leaves, bark, twigs and nuts. Oval, sharp-pointed leaves with indented edges alternate on the branches, with the largest leaves toward the center. The black or gray-brown bark shows heavy furrows and twigs are hollow inside.
Black walnuts trees grow across the United States, but the natural range is in the eastern and central part, commonly in areas with limestone soil. Because they require full sun, fertile soil and ample water, black walnut trees tend to grow singly or in small groups. Associated species include white ash, basswood, sugar maple, hickory and oak.
The presence of Kentucky coffee trees is indicative of a good growing site for black walnut trees. Leaves appear after the danger of frost passes and turn bright yellow in the fall. When these trees flower, male catkins hang from branches in the spring, followed by pear-shaped female flowers at the branch tips. Nuts form from the female flowers. Before ripening, the round nuts appear green and crinkled. In the autumn, they turn dark brown and fall when ripe. Trees produce nuts when they reach 10 years of age, but maximum production occurs at around 30 years. Black walnuts are used in baking, and the wood is used in furniture, gunstocks and veneers.