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. Thus, 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 at which 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.

Over the last 40 years or so, a fungal disease known as butternut canker has killed 80-to-90 percent of the butternut trees in the United States. Butternut canker is lethal and it spreads quickly. It has been found in every part of the butternut�s range. Most butternuts are highly susceptible to the disease, and all ages and size classes of trees can be infected. Infections appear first in the upper crown on one or two year old wood. These cankers are often elliptical in shape and slightly sunken. They will later develop an inky black center.

Butternut is a splendid, useful tree, and there is grave concern over the long-term genetic impact of this epidemic. For example, butternut is now extremely rare in the upper South, and butternut may be permanently lost from many of the Midwestern streamsides and woodlands where it once thrived. Scientists with the USDA Forest Service have, for the past 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 for reintroduction of the species to its former habitats. We are happy to report 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, and the use of these trees for breeding is being investigated. Surprisingly, a common feature of these apparently more canker-resistant trees is their thick, often darkly-colored bark. Surveys have been undertaken by both state and federal agencies to try to identify habitats in which butternut was once common so that the number and health of trees there can be monitored. These habitats are also candidates for butternut reintroduction in the future.

Some butternut trees that survived the epidemic of butternut canker were isolated and escaped infection; other trees appear to have resistance to the disease. Because butternut is now so rare, it has been difficult for us to obtain samples of butternut 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, eventually, restored. We are seeking the assistance of Indiana landowners to help us identify the location of living (and especially healthy) butternut trees. The Conservation Genetics lab of the HTIRC 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. n