European Buckthorn is a shrub or small tree that can grow to 25 feet in height and form large, dense thickets. It is a dioecious species, with male and female flowers in separate plants. Both male and female plants produce yellowish green flowers less than ¼” across with petals that are too inconspicuous to view with the naked eye. The leaves are mostly oppositely (sometimes alternately) arranged, simple, and generally egg-shaped, with small rounded teeth and hairy undersides. The trunk of an individual plant can be single or multiple and is dark gray to nearly black with a smooth, shiny surface. The fruit is a berry that ripens in August from dull green to shiny black and is about ¼” in diameter on a short stalk. Each berry contains four individual seeds.
Mice and red squirrels as well as birds, like cedar waxwings and robins, eat and disperse the seeds. But Buckthorn berries are not particularly nutritious (they are mostly carbohydrates and low in protein), so few native animals rely on them as a food source. They also can have a severe laxative effect on some birds, sometimes even strong enough to result in death.
European Buckthorn is native to much of Europe and western Asia but is an invasive species in the U.S. It is incredibly hardy and tolerant of a variety of light conditions, ranging from full sun to deep shade, though it is more common in forests than in prairies. Buckthorn also spreads quickly and outcompetes native species due to its fast growth and early leaf-out time.
In the Arb:
Buckthorn is ubiquitous in the Cannon River floodplain and is common in most wooded areas in the Arboretum. A large amount of time and energy is spent trying to contain its spread each year by the Arboretum staff.