Wood of the Week: Walnut

Botanical Background:

The Walnut/Butternut genus contains 15 species which grow in South America [6], Eurasia [4] and North America [6]. The word juglans is the classic Latin name of walnut, meaning nut of Jupiter.
The North American species of Juglans are:
Juglans californica-California black walnut, California walnut, southern California walnut
Juglans cinerea a,b -butternut
Juglans hindsii-California black walnut, hinds black walnut, northern California walnut
Juglans major-Arizona black walnut, Arizona walnut, little walnut, Mexican walnut, western walnut
Juglans microcarpa-Arizona walnut, dwarf walnut, little walnut, Mexican walnut, river walnut, Texas black walnut, Texas walnut, western walnut
Juglans nigraa -American walnut, American black walnut, black walnut, burbank walnut, eastern black walnut, eastern walnut, gunwood, Virginia walnut


Walnut is native to United States. The only parts of the contiguous 48 states that where Walnut does not normally grow is the southern tip of Florida, the southern tip of Texas, Costal California, and the northern portion of the central high plains. It also grows in southern Ontario, Canada. The species native to North America, American black walnut, was first known as Virginia walnut and is believed to have been planted in England in 1656.
Black walnut is among the most characteristic midwestern trees. Though an early successional, intolerant species on rich sites, it persists late enough in forest succession to be a component of many forest types. It is abundant in hedgerows and old fields, as well as river bottoms and coves. In the open, walnut has a short main stem with a broad crown. With even moderate competition, walnut forms a tall, stately tree. On poor sites, walnut will become established and persist, but will not become a canopy tree and is eventually snuffed out by competition
Larry Frye, executive director of the American Walnut Manufacturers Assn., in Zionsville, Ind., said that walnut has been a popular furniture wood around the world because of, among other things, its inherent durability. Since Colonial times it has been transformed into beautiful furniture designs and is found in many heirloom and antique pieces. Walnut is popular for architectural woodworking and decorative panels and is considered to be one of the finest cabinet woods in the United States. It is one of the few woods that improves with age, finishing beautifully and developing a rich patina as the years go by — a fact that has earned it the nickname “the aristocrat of American woods.”
Another possible reason for its nickname is its statuesque appearance. Walnut is one of the largest hardwood trees found in the United States and, of the two species of walnuts, the American black walnut grows taller than its European cousin. Another difference between the two species, Frye said, is that American black walnut will darken with age, while the European walnuts may become paler with exposure.
A related species is Juglans cinerea or butternut, a lighter colored hardwood that is sometimes stained to resemble black walnut.
Walnuts average in height between 100 to 150 feet with diameters of 4 to 6 feet. Average weight is 40 pounds per cubic foot. The sapwood of black walnut is nearly white, while the heartwood is light brown to dark, chocolate brown, often with a purplish cast and darker streaks. The wood is heavy, hard, and stiff and has high shock resistance.
Black Walnut is a moderately hard wood with a specific gravity of .51 per cubic centimeter when dry. Tangential shrinkage is 7.8% and radial shrinkage is 5.5%

Working Characteristics:

Black walnut is one of the great North American hardwoods. It can be anything from a mixture of dark brown and much lighter wood to a solid board of very dark, almost purplish, brown. American black walnut can be found with both a straight grain, or a distinctive, highly figured grain. Curly and wavy figures can produce interesting looks in veneers such as walnut butt, crotches, burls, fiddleback, leaf, and straight stripe. The most interesting type of black walnut is called "crotch walnut". This is wood taken from the "crotch" of a tree, an area where two large limbs grow from a common trunk. This wood is often spectacularly figured mixing dark brown and much lighter wood in very intricate patterns. When finished with tung oil, crotch walnut often has a very three-dimensional, shimmering quality that you have to see in person to truly appreciate.
Herbert Edlin and Maurice Nimmo, authors of the book, The Illustrated Encyclopedia of Trees, write that the unusually grained wood known as burr walnut “fetches very high prices as veneer; these burrs are large swellings on the trunk caused by abnormal cambium growth owing to infection by fungi, bacteria or other agents. This is an interesting example of diseased wood being more valuable than healthy timber.”
Besides being a beautiful cabinetry wood, walnut is an excellent choice for carving and lathe work. It is also a common choice for gunstocks. “Walnuts are indispensable trees for gunstocks,” said Hugh Johnson in The Encyclopedia of Trees. Because of the woods’ weight, elasticity and smoothness of touch, walnut handles a gun’s recoil better than any other wood.
Black walnut loses moisture very slowly during air drying. Kiln drying is also a slow process with American black walnut. For machining purposes, black walnut is rated hard, stiff, very resistant to shock and suitable for steam bending. Works well with machine and hand tools. It has an inherent oily nature and will cut cleanly and finish beautifully. Can be polished to high sheen. Nails and holds screws well. Glues well.

Rated as very resistant to heartwood decay–one of the most durable woods, even under conditions favorable to decay.

Interesting Walnut Trivia:

American black walnuts contribute other “products” to the American economy. The bark of the trees and the husks from the Butternut is used to manufacture yellow dyes. Wood Technologist, Jon Arno tells me that Confederate army during our Civil War used yellow butternut dye for the trim on their uniforms and this led to a slang term of the time where a confederate soldier was referred to as a "butternut." The walnut shells can be used in glues, plastics and for cleaning solutions. Then, of course, the trees yield a popular treat — walnuts. Both American and European species yield edible walnuts; The English Walnut, Juglans regia was brought to this country specifically for nut growing and is widely planted for that purpose in California and Oregon. Although the shells of the black walnut trees are thicker and harder than the English or European walnuts, some growers have developed thinner shelled varieties. Walnuts from both species are typically harvested by shaking the tree.