PlantaeDB Logo
Login Sign-up

Genus Cephalocereus in Family Cactaceae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

Cephalocereus (family Cactaceae, subfamily Cactoideae) comprises approximately four species of columnar cacti endemic to Mexico, with typical occurrences on dry, limestone hills, outcrops and thorn-scrub from sea level to mid-elevations. The type species is Cephalocereus senilis (Haw.) Britton & Rose, commonly cultivated as the “old man cactus.” The genus is distinguished by a tree-like, often tall, columnar habit that remains solitary or sparingly branched; the apex is densely covered with long, soft, white hair (a cephalium) that develops laterally or terminally with age. Stems are ribbed with radially arranged areoles bearing spines; leaves are modified to scales and stipules are absent. Flowers are nocturnal, large, funnelform to bell-shaped, pinkish to cream, produced in the cephalial wool; the perianth is widely spreading; the flower tube bears scales with hairs or wool, the ovary is inferior, and the fruit is fleshy with black seeds dispersed by birds or bats. Cephalocereus occurs across eastern and southern Mexico, with local centers of diversity and several narrow endemics restricted to specific states and limestone formations; species are typically encountered in tropical dry forest, thorn scrub and cactus associations.

Pollination and seed dispersal are inferred from floral and fruit traits typical of columnar cacti, while documented studies specific to Cephalocereus remain scarce; no base chromosome number is firmly established here. In taxonomy, Cephalocereus is a relatively small genus defined by the conspicuous, persistent, woolly cephalium and the associated flowering habit, historically segregated from related columnar cacti by Britton & Rose and later authors. While the genus remains widely accepted in contemporary treatments (Hunt, 2016; WFO, 2024; POWO, 2024), some authors merge it into Cereus or treat the complex under the synonym Pilocereus (Anderson & Sánchez, 2012), creating an unresolved alternative circumscription. Conservation concerns centre on habitat loss and over-collection for horticulture, with the widely cultivated C. senilis listed as endangered in national assessments; targeted monitoring of remaining wild populations is needed.

Pick a Species to see its components: