• 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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