Black walnut, also known as Eastern black walnut and American walnut, occurs in small groves in well-drained but moist and fertile alluvial soils throughout the Eastern United States. The tree naturally occurs throughout the East and Midwest except in the Mississippi Valley and Delta and the sandy coastal plain of the Southern United States. Since the tree most often occupied fertile soils, early settlers keyed on the walnut groves as indicators of the best soil for farming. Black walnut may grow as tall as 75 to 100 feet and two to four feet in diameter and grows well from planting zones 5 to 8; however, the highest concentration of quality trees are in the Midwestern states. It is intolerant of shade and protects itself from competition by emitting a chemical concentrate known as Juglone which inhibits growth in a number of plants. Juglone is found in all parts of the tree, but the highest concentrations are in the roots.The pollen and sawdust of black walnut is known as a strong allergen and can adversely affect horses and dogs if the sawdust is used as bedding material, so dispose of black walnut sawdust carefully.
The USDA’s Silvics of North America calls the black walnut “one of the scarcest and most coveted native hardwoods.” Black walnut was the wood of choice for fine furniture manufactured in the United States until the late 18th century.The wood was used extensively for gunstocks and furniture, but with increased demand it is now most often cut into veneer. The popularity of black walnut led to its eventual decline.The best and straightest of trees were harvested, leaving only the short and limb-laden trees to carry on the gene pool. Research was begun in the mid 20th century to select better trees for replanting, and the better quality trees are once again available. The edible nut of black walnut is widely known, but surprisingly, the shells of walnuts are widely used as well. During World War II, airplane pistons were cleaned using ground walnut shell blasted against the pistons using high air pressure.
The tree has been planted in other areas of the country for nut production. However, planting them beyond their native range has led to problems with disease and insects.