Rhamnus cathartica (Common Buckthorn)
|Also known as:|
|Life cycle:||perennial woody|
|Habitat:||part shade, shade, sun; moist to dry; woods, woodland edges, fence rows, waste areas,|
|Bloom season:||June - July|
|Plant height:||to 20 feet|
|Wetland Indicator Status:||GP: FACU MW: FAC NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Clusters 1 to 1½ inches across, appearing with leaf buds in the axils of new growth, along outer branches and branch tips, with about 10 flowers per cluster. Male and female flowers are typically on separate plants (dioecious). Flowers are yellowish green, less than ¼ inch across with 4 prominently spreading lance to narrowly triangular sepals, the males with four erect greenish stamens and the female with a single style, the tip 4-parted. Both male and female flowers have petals though they are too inconspicuous to easily observe with the naked eye.
Leaves and bark:
Leaves are mostly opposite or nearly so (occasionally alternate), simple, generally egg shaped, 1 to 2¼ inches long and ¾ to 1½ inches wide, rounded or tapered at base, the tip also rounded or tapered to a small abrupt point, the edges with small rounded teeth, surfaces sparsely hairy to hairy on the underside, on a ½ to 1¼ inch hairy stalk. The 3 or 4 lateral veins per side are strongly curved mid-blade towards the tip. Notably, the leaves do not change color in the fall, persisting green into late fall while everything else around them has shed their leaves for the season.
The trunk can be single or often multiple; a single trunk can be over 6 inches in diameter. The bark is dark gray to nearly black with a smooth, shiny surface that becomes scaly with age, thin with a bright yellow-orange cambium (layer of tissue just under the bark) and deep orange heartwood. New growth is green or brownish green, often smooth or with minute hairs, the second year twigs turning a dusty brown, older branches shiny gray green with scattered whitish, horizontal lenticels (pores).
The tip of of twigs often form a short, straight thorn with two elongated, brown scaly buds on opposite sides that curve in towards the tip and look similar to a deer hoof and from which the common name buckthorn is derived.
Fruit is a berry that ripens from dull green to shiny black, about ¼ in diameter on a short stalk, with purplish flesh surrounding 4 seeds in the center. This species' incredible propensity to proliferate across the landscape can be contributed to birds, in particular the robins, who love its fruit and spreads the seed everywhere through their droppings.
Few species have introduced Minnesotans to the concept of invasive species like buckthorn. Even as recently as the early 1990's, it was still relatively infrequent across the broader landscape. Then it finally reached the point of exponential population growth and suddenly it was everywhere. At that time (and still today), many people were unaware of the threat until it had already cobbled up much of their fence rows, woodlots and even their backyard landscapes. It was listed as a restricted noxious weed in Minnesota in 1999. Control is difficult due to its shear numbers. Smaller trees and seedlings can be uprooted but it is nearly impossible to clear large acreages without resorting to herbicides to kill the roots systems of large established trees. Even after a thorough clearing, a persistent seed bank and new arrivals from surrounding unmanaged areas require long term monitoring and management strategies that must necessarily include period prescribed burns for large areas. It is discouraging that there is now an entire generation of young adults for whom a relatively open and diverse woodland is unfamiliar. While some scoffers insist this “new normal” will be accepted as well as our recently lost, diverse forest lands, I don't foresee the day when people will make plans to travel north in the autumn to observe the annual display of dark, impenetrable, drab green Mirkwood-like forests.
Dormant identification is important for this species as many control projects are undertaken in the winter months. In late fall and early winter the persistent green foliage is the most standout characteristic. Later look for the nearly opposite brown buds with the short thorn between them on the tip of twigs, and the blackish gray bark, often shiny on the branches but peeling and corky on the lower stem, the lenticels sparse and somewhat obscure. Scraping the thin bark reveals a distinctive bright yellow-orange cambium underneath. When pulled from the ground the shallow, very fibrous roots are black throughout. Native Prunus species may be present in buckthorn infested land and can be confused with buckthorn when dormant, particularly Black Cherry (Prunus serotina). The twigs of Black Cherry are lighter brown and more finely structured with small, alternate reddish brown buds and no thorns, where buds of Common Buckthorn are opposite or nearly so. The lower bark on younger cherry saplings can be black and peeling corky but the smaller branches are typically much shinier with often very prominent horizontal white lenticels, and the cambium underneath is greenish white when freshly scraped. Cut broken branches also give off a very strong bitter almond odor when cut or crushed.
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- scaly bark of mature shrub
- more flowers
- more leaves
- Common Buckthorn vs. Cherry (Prunus spp.) leaves
- Buckthorn cambium colors vs. Black Cherry
- Buckthorn wood colors vs. Black Cherry
- Buckthorn branches vs. Black Cherry
- Mirkwood forest - woodland invasion
- a wall of Common Buckthorn
- Common Buckthorn in a home landscape
- once a nature preserve, now a buckthorn preserve - all that's green is buckthorn
- berry-laden shrub
- Common Buckthorn branches
- Common Buckthorn seedlings
Photos by K. Chayka taken in Anoka and Ramsey counties. Photos courtesy Peter M. Dziuk taken at locations across Minnesota.
Have you seen this plant in Minnesota, or have any other comments about it?