Cephalocereus senilis is native to Mexico. It grows in xerophile scrubs in calcareous canyons (from the limestone hills of states of Hidalgo to Veracruz).
Cephalocereus is a columnar, erect cactus. It grows an individual or basally branching stem up to 10 m high. Stem is light to bright green, intensely ribbed. When it gets 6 m high, it starts to produce from the top a pseudocephalium: this is a dense, white hairy mass developed by the flowering areoles. Young cactus present a conspicuous silvery-white coat, that older plant lose aging; anyway, hairs are modified spines, and hide sharp yellow central spines. After 10-20 years of life, flowers may bloom on the pseudocephalium: they are nocturnal, in a red, yellow or white colour.
Cephalocereus is an easy-to-grow cactus. It needs a fertile, well drained soil mix, and a regular, aboundant watering: let the soil get dry before watering again. Feed it monthly with a balanced fertilizer: the Cephalocereus will grow fast and healthy with a good amount of water and regular feeding during summer. If grown outside, it will need full sun exposure; inside, bright light with some direct sun. During winter, let it in a total rest in a cool luminous place. Avoid temperatures lower than 10°C (but it is theoretically hardy to 0 °C).
Propagation can be done by cuttings or by seeds. Seeds need high humidity leves, a well-draining soil and a good amount of water and light to germinate fast.
Cephalocereus senilis owes its name to its white hairy pseudocephalium, which makes it look like an old man.