Old Man Cactus
Cephalocereus senilis
Family: Cactaceae
This is a plant many people only know from container-grown plants in cultivation. As such, they will often be only a few feet tall. But this is a columnar cactus that can get from 15 to even 50’ tall! The most striking feature is the shaggy coat of long, a trait that lends the plant its common name Old Man Cactus. The white hairs serve to protect the plant from the sun. Stems are usually unbranched. Stems are usually singular and unbranching, though old plants may branch at the base of the plant. The flowering areoles (organs that flowers emerge from on cactu) develop an abundance of wool which forms a dense mass called a pseudocephalium at the top or on one side near the top. The flowers are nocturnal and can be red, yellow, or white. The plant may not flower until 10–20 years old. The fruit usually are small, obovoid, and red.
Plants can tolerate full sun, but plants grown in a lot of shade in greenhouses will need to be slowly acclimated. Part sun or even bright shade works for this plant. Water monthly in summer, and avoid watering in winter. Young plants are more frost tender and should be protected. But plants in the ground can tolerate much more cold, though how much is not really known. There is a tall plant (about 10’ down the street from our retail space that seems to tolerate temperatures at least into the mid 20s°F.
Container plants should be watered about once or twice a week in summer, and maybe lightly watered once a month in winter if no rain occurs.
The flowers are pollinated by moths and bats. The fruits are eaten by all sorts of birds, or ants.
The genus name Cephalocereus is derived from the Greek kephale (head) and the Latin cereus (wax taper, candle). The species name senilis is Latin for old man. There are 17 species of Cephalocereus native to Mexico.
Native to Hidalgo and Veracruz in central Mexico. It is threatened in the wild, but widespread propagation and popularity in cultivation have reduced the demand on wild populations.
