Flowering and fruiting

A butternut

Like other members of the family Juglandaceae, butternut's leafout in spring is tied to photoperiod rather than air temperature and occurs when daylight length reaches 14 hours. This can vary by up to a month in the northern and southernmost extents of its range. Leaf drop in fall is early and is initiated when daylight drops to 11 hours. The species is monoecious. Male (staminate) flowers are inconspicuous, yellow-green slender catkins that develop from auxiliary buds and female (pistillate) flowers are short terminal spikes on current year's shoots. Each female flower has a light pink stigma. Flowers of both sexes do not usually mature simultaneously on any individual tree.

The fruit is a lemon-shaped nut, produced in bunches of two to six together; the nut is oblong-ovoid, 3–6 cm (1+1⁄4–2+1⁄4 in) long and 2–4 cm (3⁄4–1+1⁄2 in) broad, surrounded by a green husk before maturity in midautumn.

Fossilized Juglans cinerea (fossil white walnut) in Pleistocene glacial sediments, Michigan

Soil and topography

Butternut grows best on stream banks and on well-drained soils. It is seldom found on dry, compact, or infertile soils. It grows better than black walnut, however, on dry, rocky soils, especially those of limestone origin. Butternut's range includes the rocky soils of New England where black walnut is largely absent.

Butternut is found most frequently in coves, on stream benches and terraces, on slopes, in the talus of rock ledges, and on other sites with good drainage. It is found up to an elevation of 1,500 metres (4,900 ft) in the Virginias – much higher altitudes than black walnut. The nuts are eaten by wildlife.^[7]

Associated forest cover

Butternut is found with many other tree species in several hardwood types in the mixed mesophytic forest. It is an associated species in the following four northern and central forest cover types: sugar maple–basswood, yellow poplar–white oak–northern red oak, beech–sugar maple, and river birch–sycamore. Commonly associated trees include basswood (Tilia spp.), black cherry (Prunus serotina), beech (Fagus grandifolia), black walnut (Juglans nigra), elm (Ulmus spp.), hemlock (Tsuga canadensis), hickory (Carya spp.), oak (Quercus spp.), red maple (Acer rubrum), sugar maple (Acer saccharum), yellow poplar (Liriodendron tulipifera), white ash (Fraxinus americana), and yellow birch (Betula alleghaniensis). In the northeast part of its range, it is often found with sweet birch (Betula lenta) and in the northern part of its range it is occasionally found with white pine (Pinus strobus). Forest stands seldom contain more than an occasional butternut tree, although in local areas, it may be abundant. In the past, West Virginia, Wisconsin, Indiana, and Tennessee have been the leading producers of butternut timber.

Diseases

Butternuts killed by butternut canker

Conservation

The species is not listed as threatened federally in the US, but is listed as "Special Concern" in Kentucky, "Exploitably Vulnerable" in New York State, and "Threatened" in Tennessee.^[10] This species is also listed as "Endangered" in Illinois.^[11]

The Committee on the Status of Endangered Wildlife in Canada placed the butternut on the endangered species list in Canada in 2005.^[12]

Approximately 60 grafted butternut trees were planted in a seed orchard in Huntingburg, Indiana, in 2012 as part of a larger effort by the USDA Forest Service to conserve the species and to breed resistance to butternut canker disease. Forest Service staff from the Hoosier National Forest, the Eastern Region National Forest genetics program, the Northern Research Station, and the Hardwood Tree Improvement and Regeneration Center at Purdue University are involved in the project.^[13]

As food

The butternuts are edible^[18] and were made into a butter-like oil by Native Americans^[19] for various purposes. The young green nuts, while still soft, can be pickled; Bradford Angier recommends this be done with a change of salt water every other day for a week, and a subsequent seasoning of at least two weeks.^[19] The sap can be used to make syrup.^[19]

Lumber

Butternut wood is light in weight and takes polish well, and is highly rot resistant, but is much softer than black walnut wood. Oiled, the grain of the wood usually shows much light. It is often used to make furniture, and is a favorite of woodcarvers.

Fabric dye

Butternut bark and nut rinds were once often used to dye cloth to colors between light yellow^[4] and dark brown.^[20] The husks contain a natural yellow-orange dye.^[7] To produce the darker colors, the bark is boiled to concentrate the color. This appears to never have been used as a commercial dye, but rather was used to color homespun cloth.

In the mid-19th century, inhabitants of areas such as southern Illinois and southern Indiana – many of whom had moved there from the Southern United States – were known as "butternuts" from the butternut-dyed homespun cloth that some of them wore. Later, during the American Civil War, the term "butternut" was sometimes applied to Confederate soldiers. Some Confederate uniforms apparently faded from gray to a tan or light brown. It is also possible that butternut was used to color the cloth worn by a small number of Confederate soldiers.^[20] The resemblance of these uniforms to butternut-dyed clothing, and the association of butternut dye with home-made clothing, resulted in the derisive nickname.

Fishing

Crushed fruits can be used to poison fish, though the practice is illegal in most jurisdictions. Bruised fruit husks of the closely related black walnut can be used to stun fish.^[21]