Distribution, Description & Growth
American Black Walnut (Juglans nigra) is one of the most valuable and unique species of hardwoods. Because of its rich, brown, lustrous heartwood with a grain pattern falling in somewhere between the grainy hardwoods, such as oak and the uniform textured woods such as maple and poplar, walnut wood became prized for furniture, interior finish, gunstocks, paneling, novelties and many other items. Walnut wood has a natural resistance to decay and insects. Because of the heavy use and wasteful cutting over the years, choice black walnut trees have become scarce and the price of logs has greatly increased.
Black walnut trees range from the East Coast to the Great Plains and from Texas and Georgia north to central Iowa, Minnesota, Wisconsin, Michigan, and southern Ontario, Canada. But the best quality walnut trees are found primarily in the central states regions from Ohio to Iowa. The walnut species prefers deep, rich, moist soils. The best trees are frequently found on flood free ledges just above stream banks. Black walnut typically grows as scattered individual trees or in small groups in mixture with a wide variety of other hardwoods. Black walnut is usually not found in pure walnut stands, it frequently appears with yellow poplar, white ash, black cherry, basswood, beech, sugar maple, red oak, and hickory trees. Other common associates include elm, hackberry, green ash and boxelder.
Mature black walnut trees can grow to 100 to 120 feet in height and up to 30-40 inches in diameter. Forest grown trees are generally straight and limbless, whereas open-grown or city/urban trees are frequently forked and limby.
Black walnut has one bad trait, it can poison neighboring trees, shrubs and other plants with a substance called juglone in its roots, leaves, seed husks and bark. Juglone is a substance that is selectively toxic to many plants, including tree species as well as agricultural crops. Some plants that are sensitive to juglone are: White, Scotch, and Red Pines, Paper Birch, Apple Trees and Tomato Vines.
The Black Walnut’s specific name is Juglans nigra. Black Walnut is the name commonly used, other names are American Walnut or Eastern Black Walnut.
Characteristics, Workability & Uses
The heartwood of black walnut ranks with the most durable woods, including cedars, chestnut, and black locust, even under conditions favorable to decay. Walnut is one of the few species classified as a semi-ring porous wood. The annual rings of growth are marked by many pores barely visible on the end grain at the beginning of each year’s growth and by denser growth at the end of the season. The slower growth wood seems to be softer than wood from fast growth, open-grown trees. The wood frequently contains alternate light and dark stripes that give figure effects in boards and veneer. Wavy or curly grain near knots, abnormal or irregular growth, crotches or forks and burls also result in a variety of awesome figures. Burls from very old trees are exceptionally valuable, having a bird’s eye figure on a glossy dark groundwork ranging from almost jet black to light shades of brown.
The heartwood is typically a beautiful chocolate brown color, which is not duplicated by any other species. The color can vary from more of a red color to a very dark, rich chocolaty brown, often with a purplish cast and darker streaks. The sapwood is nearly white. Forest grown trees generally have dark colored heartwood and a narrow band of sapwood not more than 1 inch wide. In open grown or urban trees the heartwood is generally lighter in color and the sapwood is about 3 inches wide. It is common practice to darken the sapwood by steaming or staining to match the heartwood. The color of walnut can also vary in uniformity throughout a board.
Walnut is rated intermediate in planning, but it is a good wood for shaping and the best of any commercial hardwood species for turning. At 12 percent moisture content, walnut weighs about 38 pounds per cubic foot. For its weight, it is a relatively strong wood. Walnut can be dried relatively easily with a moderate kiln schedule, and holds its shape well after seasoning. Black Walnut is normally straight grained, is worked easily with power or hand tools and has excellent machining properties. With figured crotch wood it is necessary to watch the direction of feed, in both thickness planers and jointers. Walnut wood finishes gorgeously, can be stained and satisfactorily glued.
Because of the unique color and grain characteristics walnut has been a prized wood for furniture, cabinets, millwork, flooring and other decorative interior applications, as well as gunstocks. Bookcases, desks, dining room tables, bedroom furniture, office furniture and many other pieces are frequently made of walnut. Because of its low movement after seasoning, walnut is particularly suitable for gunstocks. Figured black walnut stocks are prized for expensive shotguns and sporting rifles.