Trailing succulent perennials, often rooting at nodes. Leaves opposite, connate at base, triquetrous to trigonous, smooth or slightly wrinkled, the keel sometimes minutely toothed in the upper part. Flowers large, terminal, solitary or in 2s or 3s, pedicellate; sepals 5, 2 ± opposite and large, 3 small with membranous margins; petaloid staminodes and stamens numerous, both in several series, white, yellow, pink or red; styles 6–16; ovary inferior, with as many locules as there are styles; ovules numerous, parietal. Fruit fleshy, indehiscent, often edible; seeds numerous, flattened-ovoid, elliptic or oblong, c. 1–2 mm long.
About 25 species, mostly native in South Africa but also in Chile, California, Australia and New Zealand; 4 native and 3 naturalised in Australia.
Measurements in the key and descriptions of species are based on fresh material.