Black Walnut Fact Sheet
Family: Juglandaceae - Walnut family
Latin name: Juglans nigra
Common name: Black walnut
- Black walnut produces a toxin, known as “juglone”, which may inhibit the growth or kill other plants that are near them.
- The largest sources of juglone on the tree are located in the roots, but buds, leaves and nut hulls can also cause problems.
- Mature black walnut trees are usually 70-90 feet tall and 2-3 feet in diameter at breast height. However, black walnut trees can reach 150 feet tall and 8 feet in diameter if they are growing in the forest or are planted close together.
- The branches are widely spread and form a massive crown. The bark is thick and brown to grayish-black in color.
- The bark has deep furrows and narrow forking ridges. The furrows and ridges form a diamond pattern.
- The twigs are stout with notched leaf scars. They are light brown to orangish in color.
- The terminal buds are short, blunt, and covered with a few hairy scales.
- The leaves are long with 9-23 leaflets attached directly to a stout rachis without a supporting stalk.
- The rachises are covered with fine short hairs. Flowers appear in late May to early June.
- The flowers bear 17-50 stamens, but lack pistils. The fruits are 4-6 cm in diameter and spherical shaped. They can be found in groups of 2-3 or solitary.
- The fruits have a thick, semi-fleshy, husk covered with short hairs and are yellowish-green in color. The nut is corrugated with rounded ridges.
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