ST. LAWRENCE EASTERN LAKE ONTARIO PARTNERSHIP FOR REGIONAL INVASIVE SPECIES MANAGEMENT
Glossy & Common Buckthorn ( Frangula alnus, Rhamnus cathartica) are small trees or shrubs native to Eurasia. They produce pea-sized fruits that depending on the species change colors as they ripen from green to red to dark purple or black.
Buckthorn species produce dense thickets that shade out herbaceous ground species and wildflowers, thus reducing biodiversity. Buckthorn species may also provide shelter for invasive agricultural pests and pathogens like soybean aphids and oak crown rust (view a video to learn more). Buckthorn berries are easily spread long distances by birds and cause a laxative effect on wildlife that ingest them ( which helps in seed dispersal).
Habitat: woodland edges with full sun to heavy shade, fens. Most aggressive in wet soil but also found in dryer areas.
Identification:
Leaves: Common buckthorn leaves are hairless and have toothed-edged and curved veins (left two), while glossy buckthorn leaves have fine hairs, smooth edges, and parallel veins (right two).
Flowers: Common buckthorn has small yellowish-green flowers with 4 petals; glossy buckthorn has small white flowers with 5 petals. Blooms in late May
Fruit: Common buckthorn has black fruit (top), and glossy buckthorn progressively ripens from red to dark purple (bottom). Fruits are pea-sized and develop from early June through September. The seeds remain viable in the soil for two to three years.
Bark: gray or brown with prominent, closely spaced, often elongated light-colored lenticels. Below is a photo showing buckthorn bark compared to the bark of a common look-a-like black cherry.
Manual Control: Before you dig learn if there are utility lines underground. If the plant is less than 3/8 inch in diameter it can be removed by hand. Small seedlings will not resprout if removed by hand. For plants larger than 3/8 inch hand tools such as an “Uprooter” or “Root Talon” will make removal easier. Hand-pulling roots will disrupt other plants growing in the removal area. Take care to replace desired plants that are uprooted.
Controlled Burning: Effective for large stands in grasslands or savanna habitats. Burns will need to be done every two to three years and will require permits.
Mechanical: Cutting at any time will cause re-sprouting unless followed by herbicide application.
Chemical: Foliar treatment-spray leaves in the fall with glyphosate (when native plants are leafless) in temperatures above freezing. Late fall is the ideal time to treat buckthorn, because most native plants are leafless at that time, and chemicals are easily drawn toward the roots with the natural sap flow as plants prepare for winter dormancy.
Basal bark treatment-apply triclopyr or 2,4-D to uncut stems.
Cut-stump treatments– cut stems near soil & immediately apply glyphosate or triclopyr to the exposed vascular tissue (fall is the best time to apply chemical treatments).
For a chemical-free option, cover the stump with a black bag zip-tied to the stump. Bags can be purchased.
Disposal: To avoid seed dispersal, it is best to leave noxious weeds on-site. If material must be removed, contact yard waste facilities to see if they accept noxious weeds. Or burn the plant material on-site if possible.
Restoration: After removing the buckthorn, it is important to reintroduce native plants to the removal site. This not only helps to keep buckthorn from reestablishing itself, but it also helps regenerate the natural habitat. The Department of Environmental Conservation has a great list of native plants for gardening and landscaping that can be viewed online.
Photo Credits: Photo collage: top left, top right, Leslie J. Mehrhoff, University of Connecticut, Bugwood.org, bottom left and right leaves, Megan Pistolese-SLELO PRISM, thorns and sapwood, Michigan Nature Guy. Common buckthorn flower: http://www.illinoiswildflowers.info/trees/plants/cm_buckthorn.htm.Glossy buckthorn flower: National Parks Service, http://nps.eddmaps.org/species.cfm?sub=5649. Bark: Minnesota Wildflowers Field Guide, https://www.minnesotawildflowers.info/shrub/glossy-buckthorn.