Common buckthorn (Rhamnus cathartica) is tolerant of a variety of soils and is usually found in open oak woods, forest edges, disturbed sites such as openings created from downed trees, and sometimes fields and roadsides. In Vermont, common buckthorn is most widespread in the Champlain and Connecticut River valleys with the highest densities in Chittenden county followed by Addison and then Windsor counties.
Common buckthorn is a deciduous shrub that can grow quite large, up to 25 ft. tall. It has distinctive bark: dark gray or brown outer bark, often with lighter colored horizontal lines called lenticels, that peels with age and orange inner bark seen when cut.
Twigs are usually tipped with a sharp spine. Common buckthorn has dark green, opposite growing, oval leaves with three to five pairs of distinct curving veins. Leaf edges are finely toothed.
Buckthorn also has small, yellow-green flowers with four petals that grow in May-June. Small purplish black berries ripen in great numbers in late summer and persist throughout the winter.
Common buckthorn, like many invasive shrubs and trees, leafs out early and retains leaves later, allowing this species to crowd and shade out native vegetation. It also monopolizes food, water, and light effectively outcompeting other plants.
Common buckthorn berries contain a natural laxative that aids its spread but prevents the birds and mammals that feed on the fruit from absorbing necessary sugars. It is also a host for crown rust fungus and Asian soybean aphid, agricultural pests affecting oat and soybean crops respectively. Buckthorn leaves have a high nitrogen concentration, which can increase the amount of nitrogen in the soil and affect what other species can grow in the area.
Control and Prevention
Mechanical control can be effective in controlling small infestations and reducing plant vigor. Small plants can be hand pulled or removed using a weed wrench, with heavy equipment being effective for large plants. Frequent cutting or cutting followed by wrapping stumps in plastic or burlap helps reduce plant vigor and proliferation. Pulling and cutting buckthorn can be done throughout the year.
To treat large buckthorn populations either apply herbicide directly on cut stumps or spray on leaves in the fall. For large infestations or buckthorn populations in sensitive areas, a professional should be contacted for chemical treatment.
It is therefore important to remove buckthorn plants as soon as possible. Dispersal can further be prevented by burning or bagging the fruit when removing plants. When pulling smaller plants, the entire root system should be removed and hung from a branch to prevent re-rooting.
Common buckthorn is on the Vermont Noxious Weed Quarantine list, and it is illegal to purchase, plant, or transport in the state.
Native Plant Sources
Check out Native Plant Sources for places to purchase plants native to Vermont.