The butternut tree, Juglans cinerea, is a native deciduous tree across eastern North America. Also known as white walnut or oilnut, this tree is recognized for its distinctive nuts and its ecological role. It is closely related to the black walnut, sharing characteristics but with unique features.
Identifying Features
Butternut trees grow as small to medium-sized trees, typically 40 to 60 feet tall, though some exceed 100 feet. Young bark is smooth and light gray, gradually developing into flat-topped, silvery-gray ridges with age, interspersed with dark fissures.
The leaves are pinnately compound, 10 to 20 inches long, with 11 to 17 (occasionally up to 19) oblong to lanceolate leaflets. Leaflets, 2 to 5 inches long, are covered in fine, sticky hairs, giving the leaf a yellowish-green, downy appearance. A distinguishing feature from black walnut is the consistent presence of a terminal leaflet, often absent or underdeveloped on black walnuts.
Nuts are another identifying characteristic. They are oblong to ovoid with pointed ends, often lemon- or football-shaped, measuring 1.5 to 2.5 inches long. Each nut is encased in a sticky, green husk, revealing a hard, deeply ridged shell when removed. The pith inside butternut twigs is dark chocolate-brown, contrasting with the lighter brown pith of black walnut twigs. A “hairy mustache” is present above the leaf scar on butternut twigs, a feature absent in black walnuts.
Natural Habitat
The butternut tree occurs across eastern North America, from southeastern Canada (Ontario, Quebec, New Brunswick) southward through New England to northern Georgia, Alabama, and Mississippi. Its range extends westward to central Iowa and Minnesota. Butternuts thrive in well-drained, moist, and rich soils, often found in bottomlands, along streambanks, on hillsides, and within coves.
While preferring fertile conditions, butternuts can also grow in drier, rocky soils, especially those with limestone origins. They require full sun to partial shade for optimal growth and do not tolerate dense shade from competing canopy trees. Like its relative, the black walnut, the butternut produces a chemical called juglone, which can inhibit the growth of certain other plant species within its root zone, typically extending to the tree’s drip line.
Butternut Tree Uses
Historically, butternut trees provided various resources. Its wood is lightweight, soft, with a coarse grain and yellowish-gray hue. Valued for workability, staining, and finishing, the wood is suitable for furniture, cabinetry, interior millwork, and carving. Though less commercially sought than black walnut, it is used for novelties and small craft items.
Butternut nuts are prized for their sweet, rich, oily flavor. They are a food source for wildlife, including squirrels, chipmunks, and birds. Humans use them in culinary applications, such as maple-butternut candy. Native Americans traditionally boiled nuts to extract oil, used similarly to butter, contributing to the tree’s common name.
Beyond food and timber, husks and inner bark were historically used to produce natural dyes. These dyes yielded colors from light yellow to dark brown, commonly used for homespun cloth. During the mid-19th century, butternut-dyed cloth was used for Confederate Army uniforms. Additionally, the bark had historical medicinal uses, including as a laxative and in teas for ailments like dysentery and toothaches.
Current Conservation Status
Butternut trees face a severe threat from butternut canker disease, caused by the fungal pathogen Ophiognomonia clavigignenti-juglandacearum. This fungus infects trees through natural openings like buds, leaf scars, and wounds (including insect-caused). Once infected, the disease manifests as sunken, elongated cankers on the trunk, branches, and exposed roots, often dark brown to black and sometimes exuding a black, inky fluid.
Cankers girdle affected areas, cutting off water and nutrient flow, leading to branch dieback and eventual tree death. Spores are primarily spread by rain splashing from infected areas to healthy parts of the same tree or nearby trees. First identified in Wisconsin in 1967, the disease has rapidly spread throughout nearly the entire native range of the butternut in North America.
The impact of butternut canker has been significant, leading to significant population declines. In some regions, the disease has caused an 80% decrease in butternut trees, with infection rates in areas like Ontario reaching over 99% and mortality rates as high as 90% in certain areas. This widespread mortality has resulted in the butternut being listed as endangered or threatened in various parts of its range, including Canada and several U.S. states. Conservation efforts are focused on identifying and propagating naturally resistant trees, as some individuals show tolerance to the disease, and exploring hybridization with resistant species like the Japanese walnut to develop more resilient strains.