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The End of the Butternut Trees?
Article written by Keith Woeste, U.S. Forest Service and Allen Purcell of The Nature Conservancy
 

  Butternut

Butternut tree © Purdue University's School of Horticulture

Seen a Butternut?

If you know of the location of a living butternut, please contact Dr. Keith Woeste at Purdue University by calling (765) 496-6808. 

For More Information

How to Identify Butternut Canker and Manage Butternut Trees

Basic Butternut Tree Information

Butternut brochure from Ontario's Extension Office

 

Over the last 40 years a fungal disease known as butternut canker has killed 80 to 90 percent of the butternut trees in the United States. While most people have never seen a butternut, it is a splendid, useful tree. Its wood possesses a wonderful appearance and the nutmeat is sweet and rich in oils. The nut’s flavor makes them a favorite for wildlife and for people lucky enough to find and patient enough to crack them.

Unfortunately, an epidemic affecting this tree is causing grave concern. In fact, butternut is now extremely rare in the upper South, and may be lost from many Midwestern streamsides and woodlands where it once thrived. However, they aren’t completely gone from the wild and this is where you readers can be of great assistance to researchers.

Scientists with the USDA Forest Service have, for a dozen years or so, been attempting to identify butternuts that are resistant to butternut canker. Their long-term goal is to breed disease-resistant, locally adapted varieties of butternut that can be used to reintroduce the species to its former habitats.

Happily, there have been some important successes in the effort to conserve butternut. Several butternut trees have been identified that appear to have moderate to good levels of resistance to butternut canker.

Butternut (also called white walnut, lemonnut or oilnut), is a small- to medium-size tree, frequently 40 to 60 feet tall that seldom exceeds 75 years of age. It is native to the northeastern quarter of the United States and the southernmost parts of Canada. As its name suggests, butternut is a member of the walnut family, and it produces a large, thick-shelled nut, typically 1.5 to 2 inches in length. The husk or hull of butternuts is yellow-green and covered with sticky hairs. The nut inside is usually football-shaped with a distinctly pointed end and four or eight prominent seams.

The butternut tree is similar in appearance to the common eastern black walnut, but there are several features that distinguish the two species. Butternut bark usually (but not always) has wide, somewhat shallow, smooth-topped ridges superimposed on darker fissures. Butternut stems often appear shiny and olive grey, rather than the medium to dark color of walnut bark.  Butternut twigs contain pith that is dark brown and chambered, the twigs are often hairy in the spring and summer, and the bud scars (the point where last year’s leaves were attached) are surmounted by a fringe of hairs.  Butternut terminal buds are also hairy and pointed. Black walnut twigs have light-brown pith, the leaf scars have no hairs, and the terminal buds of the twigs are smooth and somewhat blunt. Simple isn’t it?

Some of the butternut trees that survived the initial epidemic of butternut canker were isolated and escaped infection. Others appear to have resistance to the disease.  Because butternut is now so rare, it has been difficult to obtain samples from across its range - even foresters now often have trouble identifying butternut. The Nature Conservancy is supporting a research effort to understand the genetics of butternut and has teamed up with Dr. Keith Woeste of the Hardwood Tree Improvement and Regeneration Center (HTIRC) at Purdue University to learn more about how butternuts can be conserved and restored. 

You can help by reporting the location of living (especially healthy) butternut trees. The Conservation Genetics lab of the HTIRC at Purdue University will test samples of the butternut trees that are identified to determine their genetic history, how they are related to other samples, and their overall contribution to the genetic diversity of the species.