Common Buckthorn

Common buckthorn (Rhamnus cathartica) is large shrub native to Europe that heavily invades wetter habitats in Montana, where it has been declared a noxious weed. Common buckthorn was recently found in Musselshell County and the Weed District wants you to be aware of this plant. The bark, roots and berries are toxic. The berries cause severe cramping and diarrhea in humans if eaten. Common buckthorn is considered a large shrub or small tree and can grow 6 to 25 feet tall. The bark is brown to grey while the inner bark has a distinctive orange or yellow color. You can expose the inner bark by scraping the bark with a knife, key or your fingernail to help identify this invasive species. The leaves are oval, glossy, dark green with finely-toothed edges Leaves stay green late into the fall, often beyond most native woody plants. The leaves are alternate on the branch where native chokecherry leaves are opposite. Young branches or twigs have downy-grey hair, maturing to dark greyish-brown and lack thorns when first growing. The twigs are usually tipped with a sharp thorn at the end of the twig when berries start to mature. The flowers are yellow-green, have four petals and develop in cluster of 2 to 5 near the base of the petioles. It has purplish-black berry like fruits that are about ¼ in in diameter. The stem of each common buckthorn berry attaches directly to the twig. Berries of native species like chokecherry form a group and this group attaches to the twig by one stem. Each berry has 3 to 4 seeds and each common buckthorn plant can produce thousands of berries each year. The seeds can stay viable in the soil for at least 5 years after dropping from the tree or by the birds who ate the berries and leave droppings at other locations allowing this invasive species to propagate in a new location. The common buckthorn plant can grow in sandy, loamy, or heavy soils and can grow in very alkaline soil. The plant spreads by seed, often disturbed by birds or small mammals who eat the fruit. Common buckthorn is susceptible to rust and powdery mildew which may be harmful to other desirable trees and bushes. Common Buckthorn can harm biodiversity in a number of ways, affecting soil quality, plant communities, and wildlife. It can change the nitrogen composition of soil making it harder for other species to survive. These changes can have long-lasting effects even after Common buckthorn has been removed. If you think you have this shrub/tree on your property please bring the Musselshell Weed District a sample of the branch into the office at 204 8th Ave East or call at 323-3740 Monday thru Thursday and we can help you identity and control this invasive species.