The Endangered Butternut

By Andrea McDowell, originally published November 3, 2010

Disease threatens unique species of tree


Messy tree says Mike 
who cut his down years ago
He shows me his butternut stump
like it’s some sort of lesson
like he gnawed it down with his teeth…
fiercely sweeping our fruitfulness from his driveway

-Glen Downie, Loyalty Management

Despite Glen Downie’s example of Mike in his poem “Butternut” from the 2008 Toronto Book Award winner Loyalty Management, what threatens the butternut tree throughout North America isn’t human. It’s not climate change, habitat loss, contaminated soil or water, or any of the usual suspects for species on the endangered list: instead, it’s a disease: butternut canker.

Butternut trees, which grow to about 21 metres and live for around 75 years, were never common in Ontario. They tolerate shade poorly, and so grow mostly in open areas rather than forests. A member of the walnut family, they produce a similar nut with a lovely flavour and a high oil content, as well as high-quality soft lumber. Butternut canker, however, is poised to wipe this species out. Recent surveys have shown that 90% of Ontario butternut trees are infected, and most of them will die within several years of contracting it. One third have died already.

Butternut canker first appeared in Ontario in 1991, and infects trees through cracks or wounds in the bark. Currently, there are no known cures or techniques to prevent the spread of the canker, so hopes focus on finding and propogating seeds from remaining healthy trees, presumed to have genetic resistance. The Ontario Forest Gene Conservation Association established a Butternut Conservation Group, taking a leading role in this effort. To help, the provincial government ranked Butternuts ‘endangered’ under Ontario’s Endangered Species Act, which prohibits any harm to any member of this species or its habitat. Translation: if you have a healthy butternut tree on your property, you cannot cut it down nor damage it in any way.

Certified Butternut Assessors, trained by the Ministry of Natural Resources, identify healthy and diseased specimens. Diseased trees often have dead branches in full sun as well as the cankers themselves, looking like black sooty stains on the grey bark. If you want or need to remove a healthy, mature butternut tree, you will need to apply and may need to have it cloned first.

Besides ensuring that healthy trees are not damaged, you can also help the butternut tree by finding and planting healthy seeds, and fall is an ideal season to try.* Simply remove the husks or soak the seeds overnight in boiled water, plant the nuts in an open area at a depth about one or two times their thickness, and mulch the seedbed. In April, remove the mulch so the soil can heat up enough for the seeds to germinate. While most seeds will germinate in their first May, some may take two or three years. Many of the resulting seedlings will also die of canker, but recovery groups hope that by planting the offpsring of resistant trees, a genetically resistant strain may result and the butternut tree could stage a comeback. Otherwise, we will have to enjoy our Butternut trees only in poetry, and not in nature.

*Pure butternut trees can be confused with hybrid butternuts, so make sure in advance of planting that your seeds are true butternuts. The Forest Gene Conservation Association may be able to help if you’re not sure.

Andrea McDowell coordinates environmental approvals and studies for wind energy projects by day and writes about environmental issues by night. This leaves twilight for hiking all over Southern Ontario’s conservation areas, parks and trails, taking photographs and cataloguing whatever she finds there at her blog Zoopolis ( She has contributed to This Magazine, Spacing, Corporate Knights, Brain, Child and Send your questions or comments about natural heritage for possible use here to:

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