Buckthorn is a woody perennial that forms dense thickets. The thickets shade out native vegetation, destroy wildlife habitats and lead to forest decline. Common or European buckthorn (Rhamnus cathartica) tends to occupy woodlands, while glossy or smooth buckthorn (Rhamnus frangula) grows in wetlands and prairies, according to the University of Wisconsin Extension. Both species spread by seed when birds eat the tree's berries, then disperse the seed through excrement. Cultural, mechanical and chemical methods effectively control buckthorn, but it may take several years to eliminate the buckthorn shrub or tree.
Identify the plant early to prevent seed production. Common buckthorn grows up to 20 feet and develops thorny twigs and leaves with teeth at the margins. Glossy buckthorn grows up to 15 feet and produces shiny leaves without teeth at the margins.
Manually remove buckthorn when the soil is moist. Use gloves to pull seedlings by hand and use a weed wrench to dig out trees or shrubs up to 1 1/2 inches in diameter. Tamp any loose soil to discourage buckthorn re-infestation or weed colonization.
Girdle large trees in sensitive wetlands to avoid disrupting the soil. Girdling involves the removal of bark and cambium tissue from the trunk, and it slowly starves the tree. Use an ax to cut a 3/4- to 1 1/4-inch-wide ring around the trunk.
Cut large buckthorn trees gradually to reduce vigor. Make an initial cut in late spring and the second cut in late summer or early fall.
Treat stems with the “basal bark” method of herbicide application. Use a handheld or backpack sprayer to apply an oil-based triclopyr formula to the bark and root collar. Cut and remove the plant after it dies, or allow it to stand and decompose naturally.
Apply the “cut stump” method of herbicide application to large stumps. Spray the stump immediately after the tree is cut to ensure the tree does not seal the cut. Use a solution that contains a 20 percent concentration of glyphosate and water or a solution that contains a 25 percent concentration of water-soluble triclopyr.
Treat stump sprouts and seedling infestations with foliar spray. Cut plants regrow rapidly and heavily after cutting. Use a non-selective herbicide such as glyphosate, or a bud inhibitor such as fosamine.