Native to the eastern United States, from Massachusetts and Minnesota south to Florida and Texas, black walnuts (Juglans nigra) are found in all but southernmost Alabama, scattered in rich bottomlands and calcareous woods. The trees are easily identified by their pinnately compound leaves composed of from nine to twenty-three leaflets; dark gray bark with deep ridges forming a diamond pattern; the "chambered" or partitioned nature of the pith when twigs are split lengthwise; and large round fruits contained in a green husk, ripening in late autumn. The fruits, when cracked open, reveal the sweet, oily nuts essential to many desserts.
Black walnuts have also been used medicinally, although with dubious effectiveness. Civil War soldiers made salve from the leaves and used the bark to staunch the flow of blood. Dye from the husks of the nuts has been used to color wood, cloth, and hair. Reputedly, a cap of walnut hulls will keep hair from turning gray, and a cloth soaked in walnut oil eases toothaches. Simply carrying a walnut on one's person was once thought to prevent rheumatism. And, according to the Doctrine of Signatures--that plants show morphological characteristics revealing their medicinal properties--the brain-like appearance of the nuts indicates that walnuts will ease whatever ails the head, including insanity.
Black walnuts also teach us a great deal about competition in the plant world. Farmers have long noted that vegetation is sparse beneath black walnut trees; certain crops, in fact, will not grow anywhere near them. We now know that the tree roots produce juglone, a powerful natural herbicide which inhibits the growth of other plants, including walnut seedlings, in a broad ring around each tree. In this process, known as allelopathy, the herbicidal properties of juglone act against many plant species--tomatoes, potatoes, alfalfa, apples, blackberries--
up to eighty feet away from the tree. Even after the death of a black walnut, enough juglone is left in the soil to seriously retard the growth of these and other
Finally, lessons can be learned from the very name of the black walnut. "Walnut" is derived from the German words meaning "foreign nut"--the idea being (correct, as it turns out) that the European species was imported from the outside, perhaps from Asia Minor. Greek mythology also comes into play because the generic name Juglans means "Jupiter's nut" and reminds us that, during the Golden Age of our existence, we humans dined on acorns, while walnuts were reserved for the gods.
So, while walking in Alabama woodlands, spend a respectful moment pausing in the shade of a black walnut. It's a lecture (or two) just waiting to happen.