About Cephalocereus senilis (Haw.) Pfeiff.
Cephalocereus senilis (Haw.) Pfeiff. is a tall, columnar cactus species that grows in clusters of stems, reaching heights of 5 to 15 meters. Individual stems are typically unbranched, as they cannot adequately support the weight of side branches. These vertical stems grow from a very large underground rhizome. Its most distinctive feature is a shaggy coat of long white hairs that resembles messy hair on an elderly man, giving the species its common name of old man cactus. Young C. senilis have an especially prominent, bright silvery white coat, but as the plant ages, the stem gradually loses this covering. The cactus produces red, yellow, or white flowers, but it does not usually flower until it is 10 to 20 years old. The long white hairs covering the stem are modified radial spines. They give many plants an almost snow-white appearance, and function to protect the cactus from both frost and intense sun. These soft-looking hairs hide tough, sharp yellow central spines, creating a deceptive harmless appearance. C. senilis is a very popular cactus for cultivation, grown specifically for its distinctive woolly look. It requires an especially well-drained soil mix, more so than most other cactus species, and needs plenty of bright sunlight to encourage thick hair growth.
