Endangered Butternuts

          Once an important source of protein and nutrition, wood, dye, and medicine for Native Americans and early Colonists as well, these important trees are becoming rare.

There is hope, but right now, not a lot of people working on the restoration project. For Dale R. Bergdahl, saving the butternuts was an integral part of his working life for 30 years as a tree pathologist at the University of Vermont. Now, in his retirement, the passion to save the butternut continues.

“When I was at UVM, we kept a long-term research project going with the U.S Forest Service back to 1983,” he said. “In following those trees that long, what we found some 75 percent mortality and very little regeneration.”

First, they lose their crown and it’s a downward spiral from there. The disease slowly kills the trees over seven to 10 years. Some survive a little longer.

Some tolerance

“We have not found any that are immune, but some are tolerant,” Bergdahl said.

Specialists select disease-tolerant trees and graft them onto black walnut rootstock in special orchards designed to produce seeds. The black walnut tree is not susceptible to the canker, but it is close enough genetically that grafts will take. But it is a slow process. Tender, new shoots are harvested in the winter, and sent to Missouri where they are grafted and returned.

“In 15 to 20 years down the road, we should have some good seed,” Bergdahl said. “But only about 10% will take. It’s a long term proposition.”

It will take decades of work, but the biggest challenge is that the money has dried up, so the Vermont project is not out actively looking for new trees.

Funding needs

“Hopefully, we’ll find funding in the next three years,” he said. “At that time, we should return to those trees in the region to see how they are doing.”

At their prime, butternut trees thrived from Quebec throughout the entire northeast quarter of this country. The trees provided a substantial source of protein and nutrition, wood, dye, and medicine for Native Americans and early Colonists as well.

The native population planted butternut trees where they routinely gathered food, enhancing their supplies. The early Colonists followed this example, cultivating the trees for their own uses. These nuts are well traveled; there is even evidence that when the Vikings visited the new world, they carried the nuts back to Greenland where their shells have been located at historic sites.

One can still find old farmsteads with clumps of butternuts growing, Bergdahl said, adding that the trees were planted primarily for the nutrition of the nut, but they also used the wood for building as it is fairly light but sturdy, and the bark and nuts make a durable fabric dye.

Rich in nutrients

“It makes sense it was a staple,” Bergdahl said. “The nut is very rich in terms of nutrient oils and was used raw, cooked, and in flours. It was also used for baby food!”

You’ll find the trees along rivers and streams, at the edge of a forest or field, or even growing among stonewalls where squirrels have hidden nuts. And Bergdahl solved the riddle of how these tiny creatures open the nuts – they wait until they start to germinate on their own which naturally splits the nut apart!

While the restoration is in a holding patter, there is a second threat to the trees. Nurseries are marketing hybrids that look and behave much like the original; so close, you have to test the DNA to actually identify them.

Genetic pollution

“We ought not to be planting butternut seedlings from these remote areas contributing to ‘genetic pollution’ of the species,” he said, adding that it is better to restore the trees that have adapted to our climate over thousands of years.

If you have a tree, don’t cut it, Bergdahl said, and let the extension service know its location.

“The biggest thing about the butternut right now is trying to conserve the material we have.”

Interview by Dorothy Read with Dale R. Bergdahl, tree pathologist UVM, April 2017.