Rhamnus japonica Maxim.
Family: Rhamnaceae
Japanese Buckthorn
Rhamnus japonica image
Shrub to 3 m tall Leaves: opposite to subopposite, with a 8 - 25 mm long, thin, hairy stalk. The blade is bright green, 5 - 8 cm long, oblong to inversely egg-shaped with a wedge-shaped base and rounded to pointed tip, finely toothed, smooth to lightly hairy beneath, with three to five pairs of veins. Flowers: borne in dense clusters on short spur stems, greenish brown, slightly fragrant. Fruit: fleshy with center seeds (drupe), black, 6 - 8 mm wide. Twigs: yellow to grayish brown, shiny, often with a sharp spine between end buds.

Similar species: Rhamnus cathartica, Rhamnus davurica, Rhamnus japonica, and Rhamnus utilis have opposite to subopposite leaf arrangements and often have spines at the tips of the stems. Rhamnus cathartica grows to 7.5 m tall. Its leaves are up to 6 times longer than the leaf stalks, are elliptic to inversely egg-shaped or nearly circular, and have two to four lateral vein pairs. Rhamnus davurica reaches 10 m tall. Its leaves are up to six times longer than the leaf stalks, are narrow oblong to elliptic, and have four to five lateral vein pairs. Rhamnus utilis reaches 3 m tall. Its leaves are more than six times longer than the leaf stalk, are narrow elliptic and often widest at or below the middle, and have five to eight lateral vein pairs.

Flowering: May to June

Habitat and ecology: Fequent in degraded open ground at The Morton Arboretum and nearby in DuPage County.

Occurence in the Chicago region: non-native

Notes: The Illinois Exotic Weed Act states that this species cannot be purchased, sold, distributed, or planted in Illinois without a permit issued by the Department of Natural Resources.

Etymology: Rhamnus is the ancient Greek name for buckthorn. Japonica means Japanese.

Author: The Morton Arboretum