Common Name: Common Buckthorn
Alternate Names: European Buckthorn, Buckthorn
Scientific Name: Rhamnus cathartica L.
Related Species: Glossy Buckthorn (Frangula alnus Mill.)
Legal Status: Restricted
Propagation and sale of this plant are prohibited in Minnesota. Transportation is only allowed when in compliance with Minnesota Statute 18.82. Although Restricted Noxious Weeds are not required to be controlled or eradicated by law, landowners are strongly encouraged to manage these invasive plants on their properties in order to reduce spread into new areas. Minnesota Noxious Weed Law.
Common buckthorn, native to Europe and Asia, is a highly invasive perennial understory shrub or a small tree that can reach heights of 20- 30 feet and 10 inches in diameter. This species was introduced to North America as an ornamental shrub and used for living fence rows and wildlife habitat. Since its introduction, it has spread aggressively across most of the northeast and upper Midwest and has become a serious threat to the degradation of native forest understory habitats where it out-competes native plant species.
- Tall understory shrub or small tree with a spreading/branched crown. Multiple stems at the base when young; eventually developing into a singular trunk/stem as it matures. Plants are either male or female.
- Main stem can be up to 10 inches in diameter with brown bark and has elongate silvery corky projections. Cut stems have orange heartwood (center/non-living) and yellow sapwood (outer/living part of stem).
- Branches contain buds and leaves that are mostly opposite or sub-opposite and terminate in small sharp thorns (up to ¼ inch in length).
- Leaves are distinctly egg-shaped, smooth, glossy, finely toothed, pointed at the tip, and have 3- 5 curved leaf veins that extend from the leaf stem to the tip. Leaves stay green late into the fall after most other trees have shed their leaf canopy, making buckthorn easy to identify at this time of the year.
- Small yellow-green, four-petaled flowers are produced in clusters near the base of the leaf stalks along the branches. Male and female flowers are borne on separate plants.
- Round berries are produced in the flower clusters of female plants following fertilization and ripen in August and September. Ripened fruit is black and shiny, highly attractive to birds, and contains 3- 4 seeds each. This adds to the ability of this species to spread quickly into new areas
- Glossy buckthorn looks similar except branches do not terminate in a thorn, leaves are alternate, toothless and oval with 8- 9 veins radiating outward from a central mid-vein. Berries tend to be a mixture of red-brown to dark-purple and black depending on maturity. Glossy buckthorn also prefers wetter habitats.
Common buckthorn occurs in a variety of upland forested habitats, but can also invade grasslands. It is typically found in forest understories, hedgerows, thickets, stream and lake edges, abandoned fields, urban landscapes, roadsides, and other disturbed habitats. This species is currently found throughout Minnesota with the highest densities in forested and urban regions of the southern half of the state. Buckthorn continues to spread north and land managers in northern Minnesota counties should be aware of this species and eradicate new populations to avoid spread into valuable forest lands and other sensitive habitats.
Means of spread and distribution
Ripened berries drop directly beneath the plants where a dense understory of seedlings is eventually produced. The fruits are also highly attractive to birds and small mammals that aid in the spread of seeds to new areas, sometimes several miles from the initial infestation. Due to the spread of seeds via birds, buckthorn is extremely hard to control and eradicate.
Common buckthorn infestations form dense, even-aged stands that crowd out native understory species and often completely displace forest understory habitats. These thick infestations also prevent the natural regeneration of forest tree and shrub species. Buckthorn 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.
Prevention and Management
- A sound management plan is necessary to manage this species and will take a commitment of a many years to ensure that the population has been eliminated or at least under control. Landowners that work together with their adjacent neighbors and local governments to develop a long-term regional management plan have the greatest success reducing this species over time. Management plans that emphasize native species restoration following treatments have been shown to sustain management well into the future and prevent new populations from developing. New infestations are less costly to control and easier to eradicate. Once buckthorn becomes well-established on a property, it is expensive to control and requires a significant amount of labor. Landowners that live adjacent to or near established buckthorn populations should continually be on the look-out to eradicate seedlings and small plants invading their properties.
- Uprooting small diameter buckthorn plants (½- 1½ inch in diameter) using a root extractor or similar tool can be effective on smaller stands. However, it is IMPORTANT to reduce any disturbance to the soil during this process, otherwise new buckthorn seedlings or other invasive plants like garlic mustard will develop in those disturbed areas.
- Early-spring controlled burns, in fire-adapted natural areas, can be a useful approach to controlling buckthorn seedlings in large forests and woodlots with dense populations. Burning every year or every other year on well-established stands may be necessary to significantly reduce buckthorn density and regeneration. Fire is not a stand-alone management option and usually works best in conjunction with herbicide applications and uprooting strategies. Make sure to contact the Minnesota Department of Natural Resources to learn more about control burning practices and regulations.
- Foliar, stem injection, basal bark and cut-stem application of herbicides that translocate their active ingredients into the root system can be very effective. Foliar treatments work best on seedlings and immature plants and should be applied early in the growing season. Stem injections, basal bark and cut-stem treatments work better on mature plants and can be applied during the late fall when buckthorn is easy to identify (green leaves still on the plants after other trees are bare) and other forest understory plants have gone dormant. Treatments will need to be administered for several growing seasons until the population is eliminated or controlled. If using herbicide treatments, check with your local University of Minnesota Extension agent, co-op, or certified landscape care expert for assistance and recommendations. There are several businesses throughout the state with certified herbicide applicators that can be hired to perform chemical applications. Buckthorn is commonly found in or around riparian and wetland habitats. If treating plants near water with herbicide, please be aware of the state pesticide laws and use only products labeled for aquatic use.