Cephalocereus is a small genus of slow-growing, columnar cacti in the family Cactaceae (order Caryophyllales), native to Mexico. Plants grow in an upright, columnar habit, reaching heights of 10 to 12 metres, and may be branched or unbranched. The light green shoots turn gray with age and can reach up to 40 centimetres in diameter. Each stem bears 12 to 30 or more vertical ribs lined with closely spaced dimorphic areoles. The central spines — up to five per areole — are yellowish to gray and up to 4 centimetres long, while the numerous radial spines are bristly or hair-like and typically enclose the shoot densely.
The genus is perhaps best known for the highly distinctive appearance of Cephalocereus senilis, the old man cactus, whose stems are almost entirely obscured by long white hair-like spines. Flowers are medium-sized, tubular to bell-shaped, and nocturnal, emerging from a woolly structure called a cephalium that forms apically or laterally on mature plants. Fruits are ovoid, covered in small scales and wool; seeds are smooth, pear-shaped, and black.
Cephalocereus was established as a genus in 1838 by the German botanist Ludwig Karl Georg Pfeiffer. GBIF recognises 14 descendant taxa within the genus.
Etymology
The genus name Cephalocereus is derived from the Greek kephalē (head) and the genus name Cereus (torch cactus), referring to the cephalium — the distinctive woolly or bristly head-like structure that crowns mature plants and bears the flowers. The genus was formally described by Ludwig Karl Georg Pfeiffer in 1838.
Distribution
Cephalocereus is native to central and southern Mexico. It grows in desert scrub habitats, specifically the Central Mexican matorral and Southern Pacific dry forests.
Taxonomy Notes
The genus Cephalocereus was established in 1838 by Ludwig Karl Georg Pfeiffer. It belongs to the family Cactaceae within the order Caryophyllales. GBIF currently recognises 14 descendant taxa under this genus at accepted status.
