Common buckthorn Rhamnus cathartica L.
Family: Rhamnaceae (Buckthorn family)
Life cycle: Perennial
Habitat: Edges of woodlands
General description: Small tree reaching heights of 20 ft and trunk diameters of 10 in. Leaves are broadly oval, pointed tip, with 3-4 pairs of curved vein; small teeth on margins. Leaf arrangement is termed subopposite since they are not evenly spaced along stems. Twigs commonly tipped with sharp spine, trees vary widely in abundance of these spines. The plant is dioecious, flowers produced in dense clusters of 2-6 in leaf axils; female plants produce clusters of black berries, approximately ¼ in diameter. Inner bark is yellow. Buckthorn leafs out earlier and holds leaves later in the fall than native trees.
Key ID traits: Oval leaves with curved veins; spines on tips of twigs; yellow cambium layer under the bark.
Similar species: Glossy buckthorn lacks the spines on twigs; leaves are not toothed, and leaves are hairy on underside.
Miscellaneous: Common buckthorn was introduced for use as an ornamental. It serves as the alternate host for crown rust of oats and the overwintering host for the soybean aphid. Aphid overwinters as eggs deposited at base of leaf buds.