common buckthorn, European buckthorn Rhamnuscathartica L.
Appearance
Rhamnus cathartica is a deciduous shrub or small tree that can grow to 25 ft. (7.6 m) in height. The bark is dark gray and the inner bark is orange (easily seen when the tree is cut). Twigs are usually tipped with a sharp spine.
Foliage
The leaf arrangement is usually sub-opposite, but examples of opposite and/or alternate arrangements are commonly found. Leaves are dark green, oval, 1.5-3 in. (3.8-7.6 cm) long, slightly serrate with 3 to 4 pairs of curving veins and a somewhat folded tip.
Flowers
Flowering occurs in the spring, with fragrant, yellow-green, 4-petaled flowers developing in clusters of 2 to 6 near the base of the petioles. Plants are dioecious (male and female flowers occur on separate plants).
Fruit
Appearing in the fall, the small, purple to black fruit are 0.25 in. (0.6 cm) in diameter. The fruit contains 3-4 seeds. Birds and other wildlife eat the fruit and disperse the seeds.
Ecological Threat
Rhamnus cathartica invades forests, prairies, and savannas in the Midwestern United States and can form dense thickets crowding out native shrubs and understory plants. It is difficult to remove and can regenerate after cutting or burning. It is a native of Europe and was introduced into the United States as an ornamental shrub.