Identify

Use iNaturalist, Tree Canada, and Invasive Species Centre resources to identify common buckthorn (Rhamnus cathartica) and glossy/alder buckthorn (Frangula alnus). 

Prepare

Prioritize buckthorns that have berries. Remove outlying, isolated trees first.

Always wear safety glasses, thick gloves, and protective clothing.

Remove

Pull seedlings under 10 cm tall by hand. 

Dig out trees under 1 m tall with a trowel or spade.

Pull out trees with stems up to 7.5 cm in diameter with a weed wrench. 

High cut trees over 5 cm diameter by sawing tree trunks at 1 to 1.5 m high. Do this in spring after they have fully leafed out. Remove any remaining branches and leaves on the stump by hand or with loppers, pruners, or a saw. In fall, remove any regrowth of leaves. Repeat the following spring. By the second fall, the stump should be dead. Remove by hand or with a spade. If not easily removable, wait another year or use a weed wrench. The seasons may be reversed, starting in fall.

Mow dense infestations of seedlings in early summer and late summer for two to three years. While quick and easy, this method also mows down native plants.

Girdling and low cutting are no longer recommended, as they can encourage vigorous regrowth unless combined with herbicides, which are only available to licensed professionals in Ontario. Tarping is difficult to set up and maintain effectively and also presents a trip hazard. 

Dispose 

Except for branches with berries or roots, stack buckthorn in a brush pile to create wildlife habitat, have it chipped by an arborist, use it as firewood, or give it to woodworkers. For city removal, chop up and tie or place in leaf bags. 

• Roots: Remove any soil and dry out upside down before disposal as above. Saplings can be left hanging from nearby trees.

• Berries: Place in black garbage bags in direct sunlight for one to three weeks before sending them to landfill. If not feasible, create a pile for branches with berries. If possible, tarp the pile. Monitor for seedlings for two years. These piles reduce the spread of berries by wildlife while minimizing labour.

Restore 

Minimize soil disturbance by tamping soil down after removal. 

Seed the area with cool season grasses (Canada and Virginia wild rye and bottlebrush rye), as they compete against buckthorn seedlings. The following year, replant with native shrubs, trees, grasses, ferns, sedges, and perennials. 

Monitor the site for at least two years and periodically thereafter.

Resources

Friends of the Mississippi River: How (and when) to use the critical period cutting method to remove invasive buckthorn

Ontario Invasive Plant Council & Invasive Species Centre: Common Buckthorn Best Management Practices Technical Document for Land Managers

Invasive Species Centre: Common Buckthorn

Tree Canada: Tree Killers - Glossy Buckthorn

iNaturalist: View Common Buckthorn or Alder Buckthorn on Ottawa, ON map