Shrub or small tree to 7.5 m tall, trunk to 25 cm in diameter Leaves: opposite to subopposite, a few alternate, with a grooved stalk 0.6 - 3 cm long and hairy above. The blades are dull dark green above, light green beneath, 3.5 - 7.5 cm long, 2.5 - 5.5 cm wide, elliptic to inversely egg-shaped or nearly circular with a rounded to broad wedge-shaped base and a rounded to pointed tip, round-toothed, with two to four vein pairs curving toward the tip, hairless to hairy beneath. This is one of first shrubs to produce leaves in the spring and one of the last to lose its leaves in the fall. Flowers: male, female and bisexual, usually on separate plants but sometimes on the same plant (polygamodioecious), borne in clusters, yellowish green, tiny, four-petaled. The petals are very tiny in female flowers. Fruit: fleshy with center seeds (drupe), solitary or clustered on short spur branches, shiny black, 5 - 6 mm wide, spherical, usually four-seeded. The one or two mature seeds are round and ridged on one side. Abundant fruit persists into early winter. Bark: gray and smooth when young, becoming dark gray with light blotches and rough with age. Twigs: gray to grayish green or brown, smooth, usually with a sharp spine between end buds. Buds: brownish black, to 6 mm long, narrow, smooth, pressed against stem. Form: irregular to rounded, with low branches.
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 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 japonica grows to 3 m tall. Its leaves are more than six times longer than the leaf stalks, are inversely egg-shaped, and have three to five lateral vein pairs. Rhamnus utilis reaches 3 m tall. Its leaves are more than six times 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. Rhamnus cathartica var. pubescens differs from the typical variety by having hairy lower leaf surfaces.
Flowering: early May to early June
Habitat and ecology: Introduced from Eurasia, Rhamnus cathartica was used as a windbreak in the 1800s. It produces many seeds, which are disseminated by birds. Dense thickets of R. cathartica replace the native understory vegetation, especially in degraded and overgrazed areas and moist disturbed woodlands. The species can be found in woodlands, savannas, prairies, abandoned fields, and roadsides throughout the northeastern and north central United States.
Occurence in the Chicago region: non-native
Notes: Rhamnus cathartica is sometimes grown as a landscape hedge, but there are many non-invasive and more ornamental shrubs that should be planted in its place. 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. Many parts of the plant contain chemicals called anthraquinones, which induce vomiting and diarrhea if eaten. This species and R. lanceolata are alternate hosts to the oat rust fungus, Puccinia coronata.
Etymology: Rhamnus is the ancient Greek name for buckthorn. Cathartica means cathartic, referring to the vomiting induced by eating the plant.
Functionally dioecious shrub or small tree to 6 m, some of the branches usually ending in short thorns; lvs mostly opposite or subopposite, or some of them alternate, broadly elliptic, oblong, or elliptic-obovate, 3-6 cm, at least half as wide, the lateral veins (2)3(4) on each side, strongly upcurved; petiole a third to two-thirds as long as the blade; fls appearing with the lvs, 4-merous; sep 2-3 mm; pet erect, lanceolate, 1-1.3 mm in staminate fls, 0.6 mm in the pistillate; style 4- fid half its length; fr black, 5-6 mm thick, commonly with 4 stones; 2n=24. Native of Eurasia, escaped from cult. at many places in our range.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.