Introduction
“Mesemb” is a common nickname for small, highly succulent members of the ice-plant family (Aizoaceae), especially the mostly southern-African groups once bundled in the old genus Mesembryanthemum. In cultivation and botany circles, the term conveniently refers to compact, stone- or cushion-forming succulents such as Lithops, Conophytum, Cheiridopsis, Faucaria, Delosperma, Pleiospilos, and Titanopsis.
The Details
Most mesembs are centered in South Africa and Namibia—particularly Namaqualand and the Karoo—with a few extending into Lesotho, Botswana, and parts of East Africa; Delosperma ranges farther and includes cold-tolerant species. They typically have opposite, very thick leaves; in many genera, the pair is fused into a single body, as in Lithops. Surfaces often show glittering “bladder cells,” the feature behind the common name “ice plant.” Physiologically, they are drought-adapted CAM plants and often follow strong seasonal rhythms; many are winter-growers synced to winter rains, though there is variation across genera and habitats.
Reproductively, mesembs are known for sun-loving, daisy-like flowers composed of many petaloid staminodes surrounding true stamens, and for hygrochastic capsules that open when wet and close as they dry—timing seed release to brief desert rains. The term “mesemb” comes from Mesembryanthemum, once a catch-all that has been split into numerous genera; the nickname persists even as taxonomy has stabilized. While Aizoaceae also includes less succulent or halophytic members (e.g., Tetragonia, Sesuvium), growers and hobbyists usually reserve “mesembs” for the compact, highly succulent types listed above.
Additional Reading: Aizoaceae
