Butternut – an uphill battle to save a part of history

Jeff Green | May 13, 2010

Kevin Hansen measuring a butternut tree.

At around 1250 AD the population in one region of what is now the State of Mississippi was denser than that of the city of London, England. The centrepieces of the civilization were massive man-made earthen mounds that were used for burial, residential and ceremonial purposes. Some were larger than the Egyptian pyramids.

To a great extent, this Aboriginal civilization drew its life-blood from the cultivation and harvesting of tree nuts.

Nuts provided a steady source of protein and were as central to the culture as rice is in Asia. The First Nations burnt the underbrush underneath the trees twice a year and made sure the trees had unimpeded exposure to the sun.

Because they could be gathered and stored, nuts protected against famine. They could be dried and stored, or left underwater in large sacks to prevent the oils from growing rancid.

Along with the hickories, chestnuts and oaks, black and white walnuts were prized. White walnuts, or butternuts, have always been a rarity. They are closely related to the more common black walnut. They are now close to extinction in this part of the world because of something called the butternut canker.

The canker was first spotted in Wisconsin in 1967. It is an air-borne fungal disease that enters the leaf scars and wounds the tree, killing the cambium layer. In time it girdles the tree and eventually kills it. There currently is no known cure for the disease.

Over the past 40 years the canker has spread throughout the north-eastern United States as well as the provinces that contain Butternut, including New Brunswick, Quebec and Ontario. Throughout Canada 60-70% of the butternut trees are found in south-eastern Ontario. Studies throughout North America conclude that 98% of the butternut in our forests contains the canker, which appears as a black oily stain over the greyish bark of the butternut. Trees heavily infected with the canker will have their bark opened and falling off.

Since 2007, a butternut recovery program has been in place in this region. The Lennox and Addington (L&A) and Frontenac Stewardship Councils have been involved in the program along with Rideau Valley Conservation.

The program has several components. Locally, Kevin Hansen from the L&A Stewardship Council has been working with landowners to identify butternut trees in Frontenac and L&A Counties, and to date 60 landowners are involved. Hansen has found a number of butternuts in Frontenac Park.

Butternuts are a solitary tree. There are no butternut groves, and since they require full sun they will not survive if they are shadowed by taller trees. They are found most often on hedgerows or fence lines. They thrive on limestone because they can draw nutrients from the rock, but they do grow on granite substrate as well. They can even be found growing out of rock piles where nuts may have been stored by squirrels.

“When you find one butternut tree you tend to find more nearby. They seem to grow in small clusters,” said Kevin Hansen. He also said they tend to grow in locations where American ginseng is found.

Butternuts closely resemble walnut trees. They are a small to medium-sized tree, which grow up to 21 metres in height and 90 centimetres in circumference.

The leaves are yellowish green, compound and fuzzy on the underside. Each leaf contains 11-17 leaflets, which lie opposite to each other on a central stalk.

Information on identifying butternut trees can be found at lrconline.com/Extension_Notes_English/pdf/bttrnt.pdf

Landowners who think they have a butternut tree on their property are encouraged to contact Kevin Hansen at This email address is being protected from spambots. You need JavaScript enabled to view it. or 613-449-0732.

The butternut canker is so well established that there are few if any uninfected trees in the region, or any trees younger than 30 years old. However, some trees seem to have resistance to the canker, and any tree that is still producing seed is being sought, since the recovery program is focused on seed collection.

Kevin Hansen's program is tied in with several projects, including a planting program at 14 sites in Eastern Ontario. As well, a two-hectare site has been set aside at the Ferguson Forest Centre (Kemptville) for a butternut archive.

Scions that have been sourced from the tops of the most healthy butternut trees that could be found are being carefully grafted onto black walnut root stock. The seedlings are left to grow in pots for two years, and are then being planted in the butternut archive grove.

“It really is an experimental project,” said Kevin Hansen, “with the ultimate goal being to produce healthy seed in twenty to thirty years' time.”

So, even if butternuts have disappeared in the region by then, the canker might die off with the trees, and the butternuts could be to the 2030s what wild turkeys have been in the past 10 years, a re-appearing species.