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 In the fall the leaves of black walnut trees turn yellow and fall from the tree before the nuts, giving the tree an interesting profile.

There was a woods bordering the backyard of my father’s house, and one year a scout from a tree harvesting company knocked on his door and offered to pay a large fee if my father allowed them to take an old black walnut tree that was on the edge of his woods. He got the money and they got hundreds of board feet of lumber. Desks, tables, and other furniture made from black walnut are so highly prized that sometimes black walnut trees are taken at night without anyone asking for permission. Tree-napping!

My father’s tree—his former tree, that is—was probably close to 250 years old, and over one hundred feet tall, which is about the maximum age and size for a black walnut. That means that it started its life before the American Revolution, or about the time that both Beethoven and Napoleon Bonaparte were born. It produced hundreds of thousands of nuts—maybe a million—during its life. I love walnut furniture, but I also love old walnut trees and I believe that venerable old trees should be spared the fate of becoming a dining room table.

Starting with the Native Americans, people have used black walnuts for relief from a wide variety of medical problems. The hull around the nut can be ground into a paste and, when thinned with a neutral salve, it can be applied to cure skin infections and acne. Eating the nuts is prescribed by natural health practitioners for many problems, from fighting cancer to protecting your heart and improving your brain. The nuts, of course, have also been food for hungry humans and used as an ingredient in many recipes.

The nuts of the black walnut are eaten by rodents—squirrels, chipmunks, mice, and voles—as well as by turkeys and bears. Over a hundred species of moths and butterflies lay their eggs on black walnuts, and when the eggs hatch the caterpillars eat the leaves. In turn, the caterpillars, which hatch in the spring, are an excellent source of protein for the birds that have just finished their spring migration from Central or South America. The small mammals that eat the walnuts are the prey of bigger mammals, making the trees the base of an ecological chain.

The leaves, twigs, bark, roots, and hulls around the nuts of black walnut trees contain a chemical called juglone, which is transmitted from the tree to the soil around the tree by several means. In spring and summer, rain leaches the juglone from the leaves and carries it to the ground. In autumn the juglone in the fallen leaves and twigs carry the juglone with them as they decompose and become part of the soil. Juglone passes directly into the soil from the roots. It is widely believed (although still in need of scientific proof) that juglone impedes the growth of many plants that might try to grow under a black walnut canopy. Affecting the chemistry of the soil to the detriment of other plants is called allelopathy, and several other plants also do this, notably Canada goldenrod, barberry, and—to a lesser extent—sumac.

Every other year black walnuts produce a bumper crop of nuts. Many nut and acorn-bearing trees also have occasional years with a bumper crop, but none of the others is as regular as the black walnuts. Oaks, hickories, and several other nut-producing trees have their exceptionally large crops every three to five years. The years of large crops are called mast years—mast is an old English term for nuts. No one knows what triggers a mast year, but it gives an evolutionary advantage to the trees that do it. If they produced the same amount of nuts or acorns every year there would be enough wildlife to more or less eat all of them every year. A mast year, however, results in more mast than the wildlife can consume, giving the trees a greater chance to reproduce.

By Jim Amon.