Cephalocereus senilis is a cactus plant commonly known as Old Man Cactus or Old Mans Beard Cactus, after the shaggy coating of long silvery-white hairs all over the plant surface. This is said to resemble unkept grey hair on an elderly gentleman and, with age, plants tend to lose this covering. These hairs are actually modified spines, an adaptation to protect the plant from adverse weather conditions such as harsh sunlight or frost. It is a columnar, clump-forming perennial cactus from the Cactaceae family. Old Mans Beard grows on average 5–15m, over a long time, it is usually unbranched and blue-green in colour. This species produces large, nocturnal pink flowers, but it may take up to 20 years before a plant reaches flowering maturity.