Common Names include: Old Man Cactus, Bunny Cactus, Old Man of Mexico, White Persian Cat Cactus
Cephalophorus senilis is a columnar and erect cactus 6 to 10 or even 15 meters high, simple or branching only basally. The flowering areoles develop an abundance of wool which confluently forms a dense mass called a pseudocephalium at the top or on one side near the top. The flowers are nocturnal red, yellow, or white, though the plant may not flower until 10–20 years old. The fruit usually is obovoid. The most striking feature is the shaggy coat of long, white silky hairs suggestive of unkempt hair on an old man and hence the name old man cactus, and similar names. The coat is a particularly striking silvery-white on the young cactus; as the plant ages, the stem begins to lose its covering. The hairs are modified spines and they make many a plant appear almost snow-white; they serve to protect the plant from frost and sun. However, the hairs are only the radial spines of the cactus; they conceal formidable sharp yellow central spines that belie the inoffensive appearance of the hairy covering.
Uses: Enjoy all year round as a houseplant or outdoors in USDA hardiness zone 11 for xeriscaping. Lifespan: Up to 200 years in the wild. Height: Up to 50 feet. Difficulty: Easy to grow with ample light and heat and tend to neglect to water. Water: During the growing season, allow the soil to dry thoroughly and then drench the plant and soil. Water very little or not at all during the winter. Soil: Use very porous, well-draining cactus potting soil rich in nutrients and minerals. Fertilizer: The potting medium should provide enough nourishment for your cactus. However, you can provide a very weak solution of fertilizer one or two times during the summer months. Growth Rate: This is a very slow-growing cactus. Kept as a potted plant, it will only put on about half an inch annually. It is unlikely to grow taller than two feet high.