October is a great time of year to spot and manage the buckthorn on your property. Buckthorn is a tall shrub or small tree that can reach 25 feet tall. It is commonly found in the understory of woodlands, fence lines, and forest edges. Buckthorn is easy to identify at this point in the season because its leaves maintain a dark green color after most trees and shrubs have changed color or the leaves have fallen off. A few samples have come into the Extension office for identification already this season, so it is important that you be on the lookout for buckthorn on your property.
There are two species of buckthorn that are invasive species here in Minnesota, the common (Rhamnus cathartica) and the glossy (Fragula alnus). Both species are not native to Minnesota and were introduced in the early 1800’s from Europe as a plant used for hedges. Land owners are encouraged to make efforts to control it on their property as it is on the Minnesota Restricted Noxious Weed List. It is illegal to sell, transport without a permit, or intentionally plant in Minnesota. In addition, the common and glossy buckthorns are an over-wintering host site for soybean aphids and should be removed in fence lines and woodlands near soybean fields to reduce aphid populations.
Other key identifying features are the common buckthorn have egg-shaped leaves with a pointed tip and stout thorns on its branches while the glossy buckthorn has oval shaped leaves that are glossy and lacks thorns on its branches. Female plants produce berries that are dark purple to black and are in clusters with one-quarter inch berries. The berries are not edible to humans, but birds readily consume them and spread the seeds causing them to be so aggressive and invasive.
Management includes hand-pulling seedlings or small trees. A tool called a weed wrench can also assist with removing plants up to 2 ½-inches in diameter. Some local SWCD or other offices have them for check-out or rent. For larger trees with 2-inch or larger diameter trunk the plant should be cut down to the ground and the stump should be treated with chemical herbicide to prevent re-sprouting. Brush or tree killing products containing triclopyr, glyphosate, or 2-4D. There are also other methods of treatment such as foliar application or basal stem or bark treatment but recognize that a foliar treatment may also kill other desired species from spray drift. Utilizing a disposable brush may be a good option to spot treat only the buckthorn. Always follow label instructions for herbicides. This can be affective if temperatures are above freezing.
For more information about buckthorn identification or control visit the Minnesota Department of Agriculture, Minnesota DNR or the University of Minnesota Extension websites.