Glossy & Common Buckthorn (Rhamnus spp.)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 are very aggressive and produce dense thickets that shade out native species. They produce dense shade that eliminates herbaceous ground species and wildflowers. Their 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.
Leaves: Common buckthorn leaves are hairless, 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 (top photo); glossy buckthorn has small white flowers with 5 petals (bottom photo). Blooms in late May.
Fruit: Common buckthorn has black fruit (top) and glossy buckthorn progressively ripen from red – dark purple (bottom). Fruit are pea-sized, and develop 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: hand pull or dig up small plants in moist soil.
Controlled Burning: Effective for large stands. Requires permits.
Mechanical: Cutting any time will cause re-sprouting unless followed by herbicide application.
Chemical: Foliar treatment-spray leaves in fall with glyphosate (when native plants are leafless) in temperatures above freezing.
Basal bark treatment-apply triclopyr or 2,4-D to uncut stems.
Cut-stump treatment– cut stems near soil in fall & immediately apply glyphosate or triclopyr to the exposed vascular tissue. Late fall is the ideal time for chemical control because most native plants are dormant at that time and the chemicals are easily drawn toward the roots with the natural sap flow.
For More Information
Photo Credits: Title photos; Top: Invasives.org, http://www.invasive.org/gist/photosp-z.html; Bottom: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org. Leaves photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org. 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.