June’s Weed of the Month is glossy buckthorn (Frangula alnus). Glossy buckthorn is a highly invasive large shrub or small tree native to Europe and Asia. It threatens riparian, wetland, and upland forest areas. Glossy buckthorn forms dense stands that crowds out and completely displaces understory habitats.
Glossy buckthorn forms multiple stems as a young plant that develop into a single trunk as it matures. The main stem can be up to 10 inches in diameter, and the cut stem is orange in the center. The leaves are alternate along the branches and do not produce terminal thorns like common buckthorn. The leaves are oval, glossy, toothless, and have veins that radiate outward from a central mid-vein. Glossy buckthorn flowers from May to July, and the berries transition from green to red to dark purple.
Though a threat to Minnesota’s forests, Glossy buckthorn can also invade a variety of upland landscapes and urban regions. By forming dense stands, it prevents the natural regeneration of forest tree and shrub species. Ripened berries drop directly beneath the plants, and are consumed by birds that then spread the seed. It is also a concern to agricultural producers because it can serve as an alternate host for alfalfa mosaic virus, oat crown rust, and soybean aphid.
Management of glossy buckthorn requires a multi-year commitment. A management plan that emphasizes native species restoration will help prevent new populations from developing.