Succulent shrubs or small trees, erect or spreading, usually much branched, sometimes forming clumps or mats. Stem segmented, segments green, sometimes reddish to purple, usually flattened, cylindrical, columnar, compressed, subglobose – obovate, smooth to tuberculate, glabrous to pubescent. Areoles woolly, wool gray, tan to brown with 0 – 15 spines per areole, sometimes setose with hair – like bristles . Glochids present at the margins of areoles. Leaves usually small, scaly, subulate to conic or cylindrical, caducous. Flower bisexual, sessile, subterminal or lateral, solitary on each areole, conspicuous. Hypanthium obovoid, truncate and depressed apically. Perianth rotate, spreading or erect, slightly zygomorphic, outer tepals green to yellow, inner ones pale yellow to orange, pink to red, rarely white, nectar chamber simple, open not covered by proximal thickening. Stamens many, filaments greenish to yellow, anthers pale yellow to yellow, much shorter than perianth, inserted on the apex of hypanthium. Style usually thick, often more or less expanded near base. Stigma 5-10. Ovary inferior. Placentation parietal. Ovule numerous. Fruit fleshy or dry, a berry, with spine bearing areoles or naked, globose or ovoid, umbilicate. Seeds usually numerous, enclosed in expanded funicles, circular to broadly oval or angular, 3 – 9 mm long, aril surface bony, trachomatous (1-4 large depression), pale, hilum basal.

A large genus of about 200 species, distributed throughout America, from S. Canada to Patagonia (Argentina). Introduced in various regions of the world including Australia, South Africa, Europe and Asia. Represented in Pakistan by 3 introduced/ cultivated species of which 2 species are naturalized.