by T’ai Roulston, Curator, State Arboretum of Virginia and Research Associate Professor, UVA
Most people are quite familiar with black walnut (Juglans nigra), a common tree of the eastern forest and a magnificent yard tree that rains down green-husked nuts in autumn. As a commercial product, it makes its appearance as a cheaper nut to make pesto, good wood for furniture, a comp
lex bitter for cocktails, and a dark stain that works equally well on furniture and human hands.
Fewer people are familiar with its close relative, the butternut (Juglans cinerea, right), which is also a large tree of the eastern forest with edible nuts and a history in furniture making. It's little known today because of its increasing rarity, wracked by butternut canker disease (below). The disease, of uncertain origin, was first found in the U.S. in 1967 but spread quickly throughout the butternut's range, causing bark splitting, trunk die-back, and eventual death. In some areas, the butternut population has declined by 80% and there is no cure for the disease.
We at the Stat
e Arboretum of Virginia are in the process of locating butternut trees in native forest sites in the region and collecting seeds to propagate and distribute to other institutions for conservation. Collecting and distributing seeds is only a first step in conserving the species. Because butternut canker is widely distributed, planting them anywhere in their native range will likely yield a diseased tree eventually. But it is a way to help look for natural resistance among individuals and provide living material that could be the basis for future conservation efforts.
Butternut's story is not so different from American chestnut, just more recent: A disease sweeps through its range knocking it back; research finds that resistant offspring are produced when it is hybridized with an Asian species (Chinese chestnut in the American chestnut story, Japanese walnut in the butternut story).
Decades of effort with American chestnut could soon lead to self-sustaining populations of the formerly dominant canopy tree of the Appalachians, whether through hybridization or through adding of a resistance gene to its genome. It is unclear what will be the path forward for butternut, but the current pathway in the wild is toward oblivion.
If you know of wild locations for butternut in the mid-Atlantic region, I would very much like to hear about them (tai.roulston@virginia.edu). Despite their recent decline, butternut trees are still found producing nuts in many areas. It is time to document, assess, and undertake efforts toward conserving them.
To hear T'ai discuss butternut decline on the PBS television show Virginia Home Grown: https://www.pbs.org/video/conservation-jvidle/