The large, deep green, lustrous leaves of black walnut give the tree a luxuriant appearance that is more suited to the tropics than to our clime, where, typically, trees are far more restrained. Indeed, the genus Juglans, which also includes our native butternut, is believed to have arisen in warmer latitudes at a time when the entire earth was warmer, about 40 or 50 million years ago. Black walnut is still happier in the central and southern parts of the U.S. than it is in the Northeast, and rich bottomland soils bring out its best.
In addition to being chilly, northern soils are a bit too acidic to allow the species to achieve its full potential. In pre-Colonial days, in its preferred habitat, trees 150 feet tall and six feet in diameter were not uncommon. The tree once was far more common, and its beautiful wood was used recklessly, for such things as railroad ties and split rail fences, simply because it is durable when in contact with soil. Those fence rails split by Abraham Lincoln probably came from walnut.
As black walnut’s virtues as a timber tree became recognized, good specimens were felled and made into solid walnut furniture, much of which was exported to Europe. Now it is so precious that nearly all decent-quality black walnut wood is turned into veneer, and this process brings out the lovely intricacies of the grain, a feature that is not so obvious in solid wood furniture.
Black walnut has long been the favored wood for gunstocks. In addition to being handsome, the wood is said to have less recoil than any other species; it does not split, warp, or shrink; and it has a satiny surface that never irritates one’s hand. In the mid-1700s, the Connecticut River valley was the center of New England’s flourishing small arms industry. Within five years of the establishment of the fledgling U.S. government’s national armory in Springfield, Massachusetts, in 1795, high-quality black walnut trees were no longer to be found in New England. Lumber was instead imported from Pennsylvania and Maryland. After 20 years of gun manufacturing, walnut for the armory’s products was being transported from as far away as the Ohio Valley, west of the Alleghenies.
While some people consider the fruits of black walnut to be a nuisance because they need to be raked up and disposed of, for others, the sweet-tasting nuts are the main reason to grow this species. The fruits are large, about three inches in diameter, and they stay on the tree after the leaves have fallen. They were an important food for the Abenaki and other Native Americans, who made a substitute for mother’s milk by liquefying the cooked nutmeats. Early European settlers used black walnuts far more than we do today, as the more easily shelled English (properly called Persian) walnuts were not available.
There is still an active black walnut industry, centered in the midwestern states, with a commercial harvest of over 50 million pounds of nuts. In addition there are countless backyard nut gatherers. There is even a market for the shells, which, when ground, make a biodegradable, non-toxic, and chemically inert abrasive that is used to polish engine parts and as an ingredient in cosmetics. The clammy outer hull has few fans as it is sticky, messy, and stains the huller’s hands with brown that can only be removed by time. Many kinds of squirrels, including the red, flying, and gray, are adept at shelling walnuts. And black walnut leaves are a favorite food of luna moth caterpillars.
Whether grown for timber or nuts, black walnut doesn’t tolerate shade, and this is one reason it thrives in the yard. Planted trees now account for almost all of the black walnut population in New England and New York. Late to leaf out and early to lose its leaves, walnut provides shade exactly when it is needed. The one- to two-foot-long compound leaves have 11 to 23 pointed leaflets. More correctly, they have 10 to 22 leaflets, as often the terminal one, for some unknown reason, is missing. The dense crowns and strong, dark trunks are striking, and a good specimen is certainly something to be proud of. A knowledgeable homeowner will supply it with much-appreciated nutrients and plenty of water, but won’t plant one near the vegetable garden, as this tree exudes a toxin, called juglone, from all its parts, which is lethal to many other plant species.