Butternut

(Juglans cinerea)

Status: Endangered (ESA & COSEWIC 2017)

Table of Contents:

Species Identification
Habitat and Biology
Similar Species
Threats/Reasons for Being at Risk
Conservation and Recovery Strategies
Why You Should Care
How You Can Help

Species Identification:

The Butternut is a deciduous tree in the Walnut family with a broad, open crown, reaching approximately 30 m in height and 90 cm in diameter at maturity. They have yellow-green compound leaves composed of 11 to 17 leaflets, with the leaflets that make up each leaf are arranged in an opposite pattern, and have one leaflet at the end of each leaf stem, making the leaves look like a feather. The leaflets have a hairy underside and a pleasant smell when bruised. The bark is smooth and grey when the tree is young and becomes rigid with age. Twigs are yellowish-orange, and flowers grow in clusters of up to 8. Fruit also grows in clusters- they are large, egg-shaped nuts composed of a seed encased in a thick, light green husk. The outer husk is covered in sticky, rust-coloured hairs.

Habitat and Biology:

The Butternut’s range spans much of Central and Eastern North America. In Canada, Butternut is found in New Brunswick, southern Quebec and southern Ontario as far north as the Bruce Peninsula. Butternut trees can be found throughout The Land Between. Butternut trees can be found as far south as Arkansas, Mississippi, Alabama, and Georgia, as well as from the Atlantic Coast west to Minnesota, Iowa, and Missouri. The largest populations of Butternuts can be found in the Appalachian Region, southern Great Lakes Region, Upper Mississippi River watershed and Ohio River watershed.

They grow in deciduous forests with Basswood, Black Cherry, Beech, and Maple trees, and prefer moist, well-drained soil over limestone bedrock. Butternut is shade-intolerant and grows in sunny locations often along forest edges or streams. It flowers from April to June, and is wind pollinated. The fruit remains on the tree until after the leaves have fallen and seeds are dispersed by gravity, water, and small animals that eat the fruit. They are a fast growing, short lived species, reaching maturity after about 20 years and rarely reaching the age of 75.

Map taken from Government of Canada: https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/butternut-2017.html

Similar Species

This species is similar in appearance to the Black Walnut. The two can be distinguished by the fact that the leaflet at the end of each Butternut leaf is as large as the other leaflets, while the leaflet at the end of each Black Walnut leaf is either smaller than other leaflets, or not present at all. The fruit of the Black Walnut is also much less hairy than the fruit of the Butternut.

Threats/ Reasons for being at Risk:

1. Butternut Canker: Butternut Canker is a fast-spreading stem and branch disease caused by the non-native fungal pathogen Sirococcus clavigignenti-juglandacearum. The fungus spreads through the dispersal of spores carried by wind and rain, and has infected almost all Butternut trees across its Canadian range. It is predicted to cause a nearly 100% decline of the population in just one generation. The fungus enters the tree through leaf scars or other wounds, and infects and kills the cambium tissues (layer of undifferentiated cells that occurs between the water transporting tissue, and the sugar transporting tissue). The death of this tissue may disrupt the nutrient flow in adjacent nutrient-transporting tissue. As the dead areas of tissue, or cankers, spread, the branches and trunk of the tree are girdled, eventually resulting in the death of the tree. While most trees die within a few years of infection, others have been found to last much longer. These trees, along with others that have not yet been infected by the pathogen, are being studied by scientists for signs of genetic resistance to the pathogen.

2. Harvesting of trees in anticipation of mortality: The removal of Butternut trees, infected or otherwise, in anticipation of mortality has the potential to outpace the threat of Butternut Canker itself. Some landowners have begun to remove Butternuts from their property, in an effort to sell them before they are infected, which would reduce the quality of the wood. Other trees are removed while they are still alive because they have been infected by the Canker. Trees that appear to be surviving in spite of infection should not be removed until they have been properly assessed by a Ministry of Natural Resources and Forestry Butternut Health Assessor, as the tree could possess some level of genetic resistance to the pathogen that is allowing it to survive. Further, a Butternut may appear to be infected with Butternut Canker, but it could be infected with another, non-lethal fungus Melanconis juglandis, that the Canker is often confused with.

Conservation and recovery strategies:

Conservation Authorities, the Federal Government, the Government of Ontario, the Forest Gene Conservation Association and many other dedicated groups are working together to initiate Butternut Recovery Programs across the region. These programs focus on landowner education and outreach, finding, monitoring and planting healthy Butternuts, assessing infected Butternuts, and seed collection from healthy Butternuts. Butternut trees in Ontario are not allowed to be removed or harmed except on private property under certain circumstances.

Why You Should Care:

Almost all of the Butternut trees in Canada are already predicted to be infected with Butternut Canker, and approximately one third of the trees in Eastern Ontario have already died, with the rest of almost the entire population expected to be killed in one generation (approximately 60 years)
It is not yet known if some trees are able to continue to grow long after being infected, since they may possess some level of resistance to the pathogen. If this is the case, scientists may be able to eventually recover the Butternut tree
In order to determine if genetic resistance exists, scientists need to be made aware of any and all Butternut trees that appear to be thriving in spite of the disease. This is where you come in! If you have a Butternut on your property, or you have come across one in your travels and report it, you could play a role in helping scientists work to recover the Butternut tree
The wood of Butternut trees is considered a specialty product and is used for interior finishing and turnery. The Butternut husk contains a tannin that can be used for dyeing fabric and making ink. Butternut is also edible and rich in omega-3 fatty acid

How can you help?

Learn how to identify Butternut and submit observations online to The Land Between, iNaturalist, the Ontario Woodlot Association (1-888-791-1103), or the Forest Gene Conservation Association. If the tree is not infected or appears to be thriving despite infection, it may have some level of genetic resistance to Butternut Canker, and may be of interest to scientists.
If you have Butternut on your property, consider removing nearby trees that are blocking light (provided they are not other Species at Risk), to allow the Butternut to have more sun exposure. Keep an eye on your Butternut trees and report any changes.
Contact the MNRF if you have Butternut on your property that appears to be infected - All Butternut trees must be assessed by a Ministry of Natural Resources and Forestry Butternut Health Assessor before they are removed, as the tree could possess some level of genetic resistance.

Additional Resources:

Government of Ontario’s Butternut Species at Risk page
Nature Conservancy Canada: Butternut information page
Learn to ID the Butternut using iNaturalist

Sources:

Government of Ontario. 2014. Butternut (Species at Risk). Retrieved from: https://www.ontario.ca/page/butternut-species-risk

Poisson, G., and M. Ursic. 2013. Recovery Strategy for the Butternut (Juglans cinerea) in Ontario. Ontario Recovery Strategy Series. Prepared for the Ontario Ministry of Natural Resources, Peterborough, Ontario. v + 12 pp. + Appendix vii + 24 pp. Adoption of the Recovery Strategy for the Butternut (Juglans cinerea) in Canada (Environment Canada 2010). https://www.ontario.ca/page/butternut-recovery-strategy#section-4

COSEWIC. 2017. COSEWIC assessment and status report on the Butternut Juglans cinerea in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii + 74 pp. https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/butternut-2017.html