The Butternut tree (Juglans cinerea) is a native deciduous hardwood tree related to the Black Walnut (Juglans nigra). Also known as White Walnut, the wood from Butternut is used for woodworking, furniture and wood trim in houses.
When I moved into an 1850s farmhouse in Beaver County, the dark woodwork in the house was assumed to be Black Walnut. After sanding, however, the wood revealed a lighter color and was identified by a local woodworker as Butternut. Shellac, which had darkened over a century, had created this disguise. As the layers of old shellac and white paint were removed from the woodwork of the house, the wooden doors, fireplace surrounds and staircase magically changed to a warm honey color, a lasting tribute to these historic trees.
Years later, oblong nuts found along the property hinted at the possibility of Butternut trees nearby. Indeed, now several Butternut trees have been found near the house and fields. Were Butternut trees harvested locally when the house was built in 1850? Are other homes in Beaver County graced with this lovely wood?
Nuts from the Butternut are similar to black walnuts, but are more oval in shape and more deeply ridged. Their smell is less pungent, and the husk is sticky and slightly fuzzy, rather than the smooth, green husk of Black Walnut. The nuts within are lighter in color and sweeter than the Black Walnut, having the highest oil content of any nut in North America. As a high-energy source, these nuts are favored by forest foragers of all types. Once gathered by native peoples, squirrels now collect this nut.
Butternut trees are somewhat smaller than the native Black Walnut. They prefer an open habitat in sandy or gravely loam soils in bottomlands along streams. However, they do not tolerate swampy conditions. Beaver County is near the center of the native Butternut habitat. Having a shorter natural lifespan than Walnuts, Butternuts live an average of 75-100 years. Like the Black Walnuts, juglone, a natural fungicide and allelopathic chemical, is produced by the roots of both trees and can impact the growth of potatoes and tomatoes nearby.
It can be difficult to distinguish between these two species. Butternuts have compound leaves made up of 11 to 17 leaflets, which are arranged in opposite pairs along a central stalk; a prominent terminal leaflet is present. Walnuts have a similar compound leaf, but the leaflets are arranged in an offset pattern along the stalk and lack (or have a very small) terminal leaf. The Butternut leaves turn yellow and drop early in the fall. The bark of Butternut is more grayish and less rough, especially in younger trees. To add to the difficulty in identity, Butternuts have hybridized with the introduced Japanese Walnut and English Walnut. It is hard to truly know a Butternut!
The Butternut tree is fading from our native woods, partly due to loss of suitable habitat and partly due to disease. It is susceptible to a canker fungus (Siricoccus clavigignenti-juglandacearum), which attacks the cambium of the bark of the tree, appearing as sooty black patches. Disease will spread through a susceptible tree and eventually the tree will die. The fungus is spread by wind, rain, insects and possibly birds. Experts have suggested that 80% of Butternut trees have died from this disease since canker was introduced into the US in 1967. Healthy trees are more resistant to disease. If you have a Butternut tree, promote healthy growth by removing shading trees to allow adequate sunlight, and provide additional water during droughts.
Canada has listed the Butternut as an endangered species since 2003; in the US, this species is considered one "of special concern." Recovery programs to save this tree have been established in Canada and the USDA Northern Research Station at Purdue University. Resistant trees may occur in nature and genetic diversity is important. Hopefully enough resistance to disease remains to allow restoration of this unique North American tree.
Kathy McClure is a master gardener with Penn State Extension in Beaver County.