Common Buckthorn (Rhamnus cathartica)

A deciduous shrub or tree from the Buckthorn Family (Rhamnaceae)

Common Buckthorn, also known as European Buckthorn, is an invasive shrub throughout all of Ohio, the greater Midwest, and in fact quite a large portion of the Eastern United States. Its ability to colonize fencerows, fields, and neglected areas, coupled with its tough constitution and rapid growth rate, allow it to quickly produce copious amounts of black fruits on relatively young female shrubs. It is spread via bird consumption and subsequent dispersal to surrounding areas, much like Amur Honeysuckle (in fact, these two foreign shrubs often occupy the same niches, displacing native shrubs and trees). The most positive aspect of this large shrub or small tree is its glossy, dark green foliage, which is usually clean throughout the growing season (that is, no diseases or pests bother it) and the leaves usually hang on rather late into autumn. Its heartwood is bright orange, and its wood strongly resists rotting.

Common Buckthorn is named for the semi-thorny nature of its short twigs, which terminate in modified spines, rather than buds. The specific epithet refers to a cathartic drug that is extracted from the bark. Specimens found in the wild may reach 15 feet tall and 15 feet wide; those limbed up and thinned of smaller trunks at the base may grow to 25 feet tall by 20 feet wide. As a member of the Buckthorn Family, it is related to other Buckthorns, including two that are used in modern landscapes.

Potential Problems - Common Buckthorn is extremely invasive via the production, dispersal, and germination of its many seeds, which female shrubs start producing at a young age. In the first two years of its life, its black roots are shallow and fibrous, making them easy to pull up (and either throw away, or transplant). In addition, Common Buckthorn serves as the alternate host for a type of fungal rust (Puccinia coronata) that devastates oats and other cereal grains. 

Common Buckthorn is highly invasive and should not be planted in Ohio.

Leaf Identification Features

Common Buckthorn has leaves that are opposite or subopposite, with veins that are unusual in that they branch in alternate fashion from the midrib, then run roughly parallel to the serrated leaf margins. Leaves may be either elliptical (left) or orbicular (right). Fall color is green or chartreuse, then abscising.

Other Identification Features

Rarely, plants that are classified as having opposite leaves in summer and opposite buds in winter, will actually tend towards having subopposite leaves and buds. While Forsythia is a convenient landscape shrub to observe this trait, Common Buckthorn is a naturalized shrub that also exhibits this character with respect to its leaves and buds.

Common Buckthorn is a dioecious species, having small yellow-green male and female flowers on separate trees. On female trees, these become clusters of small, rounded, green fruits, which change to plump black fruits by late summer. Birds relish the fruits, and spread the seeds readily to areas where they easily germinate the following spring.

The terminal buds of many twigs of Common Buckthorn are actually modified spines, and give a thorny character to this noxious shrub (three spines are shown). This shrub also has many spur shoots, from which many leaves, flowers, and fruits arise.

The young bark is smooth and shining, with brown-gray bark that has prominent small lenticels. Mature bark is also shiny, but becoming more scaly with horizontal lenticels.