Scientific Name
Juglans cinerea
The butternut is a member of the walnut genus with several features that set it apart from its close relatives. In the U.S., it is most often compared to black walnut, since the two share much of the same native range, though butternut does not extend into the Deep South. Black walnut is also familiar in Denver, where it was once moderately common before many trees were lost in the 2010s to thousand cankers disease.
Both species have large compound leaves that can reach or exceed 2 feet in length, with 11 to 25 leaflets. The twigs are stout with prominent terminal buds, and fall color is a bright yellow. In winter, like many Juglans species, the leaf scars form what is often described as a “monkey face.”
Butternut differs from black walnut in several ways. It is shorter-lived, averaging around 75 years, and produces oblong fruits in clusters of two to six. Each fruit is a nut enclosed in a sticky husk. The bark is lighter in color, though still fissured. The nuts themselves are deeply and irregularly grooved with a pointed tip. They contain a sweet nutmeat that is somewhat difficult to extract, though squirrels manage it easily. The wood is valued for furniture making, even if it does not command the same price as black walnut. In Colorado, the two champion butternuts in Fort Collins measure 71 and 56 feet, while a more typical mature height here is around 50 feet.
While butternut is not affected by thousand cankers disease, it faces another serious threat in butternut canker, a fungal disease that has devastated native populations. The two young trees at Regis have not shown signs of the disease so far, though there are no guarantees, as it may spread through multiple pathways. Butternut is rarely planted in Colorado and is not native to the Great Plains, with its natural range not extending as far west as Kansas City or Omaha.
There is also uncertainty about natural resistance within the species. One encouraging possibility is hybridization. Japanese walnut, which is highly resistant to butternut canker, was introduced to North America more than 150 years ago and has hybridized with native butternut. As a result, pure butternut trees may now be less common. If the Regis trees have any degree of hybrid ancestry, they may have improved resistance to the disease.