Rhamnus

PLANT: Shrubs to small trees, unarmed. STEMS: several to many, ascending to erect, rigid, gray to brown, pubescent to glabrous; bud scales present, 3 mm long. LEAVES: evergreen or deciduous; alternate to nearly opposite, petiolate; blades lanceolate, oblong or ovate to round, serrulate, toothed, spinescent or entire, glabrous to pubescent, pinnately veined. INFLORESCENCE: axillary, cymose, of 1-10 flowers. FLOWERS: imperfect, pedicellate; hypanthium hemispheric; sepals 4, greenish-yellow, triangular; petals 0 or 4; stamens 4; style branched. FRUITS: drupes, red or black at maturity, globose; stones 2, tan, rounded; seeds grooved. NOTES: 125 spp. (3 in AZ); cosmopolitan. (Greek: Rhamnus, ‘various prickly shrubs’). Some members are valued for medicine or dyes. The fruit is eaten by several species of birds. Rhamnus cathartica L. (Common Buckthorn) is a commonly cultivated species often armed with blunt thorns. It is readily separated from the native species by its opposite leaves, 5-merous flowers and a black drupe with four stones. This species may persist from cultivated plants. Rhamnus cathartica may also naturalize, especially in riparian areas, although there are no herbarium specimens to document this in AZ. REFERENCES: Kyle Christie, Michael Currie, Laura Smith Davis, Mar-Elise Hill, Suzanne Neal, and Tina Ayers, 2006 Vascular Plants of Arizona: Rhamnaceae. CANOTIA 2(1): 23-46.

Fls 4-5-merous, perfect or unisexual, the staminate with vestigial pistil, the pistillate with shorter or smaller stamens; pet lacking (in one sp.) or present, small, often obcordate with the sides folded about the stamen; ovary 2-4-locular; fr a drupe with 2-4 1-seeded stones; shrubs or trees with alternate or opposite, pinnately veined, usually toothed lvs and green or greenish-white fls solitary or umbellate in the axils of a few of the lower lvs of the current season. 100, widespread.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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