Control buckthorn during winter dormancy
This year's unseasonably warm winter weather and little snow cover makes woody plant control easier in home and agricultural landscapes. Removing invasive plants like buckthorn is more successful in the winter months, when the plant is dormant.
Buckthorn out-competes native plants for nutrients, light and moisture. It also degrades wildlife habitat and threatens the future of forests, wetlands, prairies and other natural habitats. Buckthorn serves as host to pests like the soybean aphid. Since it lacks natural controls like insects or disease that would curb its growth, it must be controlled.
Small seedlings may be pulled. The procedure for control of established buckthorn plants is 1.) Positively identify the tree or woody plant to control, 2.) Cut to form a stump, 3.) Treat the stump with herbicide, and 4.) Dispose of any brush that contains seeds.
Positive identification is important, but can also be difficult when trees aren't leafed out. Buckthorn usually has a tiny thorn at the very tip of most branches. Other desirable trees have a bud. If you scrape the bark of buckthorn it is usually yellowish-orange instead of cream-colored or green. Female buckthorn trees have purplish-black berries with multiple seeds per berry, compared to native trees and shrubs that usually have only one seed per fruit.
Tools for control include pruning loppers, a hand saw or chain saw, a labeled brush killer herbicide in a spray applicator or a tin can and brush. The most effective brush killers for cut stump treatments include Triclopyr as one of the active ingredients. An oil base and ester formulation is best for winter treatments. Follow label directions.
Cut the tree trunk an inch above the ground and treat the surface of the stump with the labeled herbicide. Make sure the entire bark or cambium layer is treated (edges of the stump). If any part of the exposed bark layer from the cut stump is not treated, the tree may sprout again. Properly dispose of the brush. Note that if the tree is a berry-producing (female) buckthorn, the seeds may still be viable and you will need to bag or burn the brush to minimize spread of seed.
A two-person team will be most effective. One person identifies and cuts the tree and the other, following behind, treats the stump. Rope off and work in one small area at a time to best keep track of your progress. Treated areas must be monitored for new seedlings or regrowth annually.
To learn more about buckthorn control, visit www.extension.umn.edu/go/1095.