Butternut Trees on Your Property

Butternut trees are widespread through-out Ontario, but their numbers are decreasing due to an invasive disease called butternut canker. Butternut canker was first confirmed in Ontario in 1991 and is thought to have originated somewhere in Asia. Like many invasive pathogens, it has spread quickly in Ontario. In 2005 the butternut was officially declared an endangered species by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and was subsequently awarded protection under the federal Species at Risk Act (SARA). If you want to develop, knowing how to identify butternut trees are on your property can help in determining what steps need to be taken to obtain a permit.

Identifying Butternut Trees

Do you think you might have a butternut tree on your property? Butternuts are visually similar to the black walnut and the two can be difficult to tell apart. Here are some tips on how to identify a butternut when compared to black walnut:

Butternuts and black walnuts both produce large nuts covered in a leathery, green, strong-smelling rind. The difference between the two species lies in the shape of the nuts. Black walnuts have a very spherical nut shape, while butternuts are far more elongate/ovoid.

Drawing of a comparison of Black walnut and Butternut seeds.
A comparison of Black walnut and Butternut seeds (Drawing Credit: Candice Talbot, 2019).

Another easy way to tell the two species apart is by looking at the leaf scars on the twigs. The butternut leaf scar looks like a comical monkey-like creature with big bushy eyebrows. The black walnut is another creature altogether, lacking eyebrows and instead having a defined v-shaped notch in its forehead to make way for the bud. Note that in the butternut, the bud is far above the creatures head.

Comparison drawing between black walnut and butternut seed.
Drawing depicting leaf scaring on Black walnut and Butternut seeds (Drawing Credit: Candice Talbot, 2019).

The leaves of butternuts and black walnuts also differ. Black walnut leaves tend to have more sets of leaflets than butternuts. Butternut leaflets also tend to be much larger in size than black walnut leaflets. One of the key differences though, is the presence or absence of a terminal leaflet (the single leaflet at the tip of the leaf). Black walnuts often have a very small terminal leaflet, or no leaflet at all. Butternuts on the other hand, have a definite terminal leaflet which is not reduced in size.

Comparison of black walnut and butternut leaflets.
Comparison drawing of Black walnut and butternut leaflets (Drawing Credit: Candice Talbot, 2019).

In addition to the above there is another identification method. Butternuts affected by lethal cankers can present themselves with black, sooty and/or wet looking wounds on usually pale grey bark.

Photograph of lethal butternut cankers.
Sooty black Butternut cankers (Photo Credit: Candice Talbot, 2019).

Removal of Trees  and What You Should Know

Since butternut trees are a protected species, special consideration must be given before the a tree is removed or damaged. If anyone wants to remove or may damage a tree, an application for a permit to do so must first be completed. A qualified butternut assessor then must first determine what Ontario Ministry of Natural Resources and Forestry (OMNRF) health category the tree falls into. Butternut health assessors are granted certification to do this through training from the OMNRF.

Butternut Categories

The butternut assessor applies each butternut tree a specific category. Health assessments result in a tree falling into one of three categories.

  • Category 1: In the advanced stages of disease as a result of butternut canker. This category may also be referred to as “non-retainable”. These trees can be harmed or removed.
  • Category 2: The tree does not have butternut canker or disease is not as advanced. This category may also be referred to as “retainable”. These trees can be removed up to 10 at a time, but mitigation must occur in the form of planting and monitoring seedlings to offset the loss of a retainable tree.
  • Category 3: Could be useful in determining how to prevent or resist butternut canker. This category may also be referred to as “archivable”. These trees cannot be removed since they likely have a resistance to the canker. These trees are of significant ecological importance.

Consequences of Unauthorized Butternut Removal

The removal of Category 2 and 3 butternut trees on your property may result in large fines from the OMNRF, as well as possible fines from your local municipal government. Niblett Environmental Associates Inc. can assist you to protect this imperiled tree species. We are always available for consultation and our qualified butternut assessors can complete the required assessment to decide the fate of the butternut tree. Like all Species at Risk, we must all make an effort to preserve healthy plants, trees and animals that are at risk so that they can continue to exist for future generations to enjoy.

Other Sources of Information

  • Butternut: Ontario Recovery Strategy Series, OMNRF 2013. (PDF)
  • Butternut Assessment Guidelines: Assessment of Butternut Tree Health for the Purposes of the Endangered Species Act, OMNRF 2011. (PDF)