Old man cactus (Cephalocereus senilis). The wiry, white "hairs" of old man cactus are an adaptation to protect the cactus from the harsh desert sun. Caution: Although it looks touchable, avoid petting its inviting coat of hair as sharp thorns lie underneath. Old man cactus prefers a very well-draining, sunny location; the more sunlight it receives, the longer and thicker its "hairs" will grow. This erect cactus can grow to 20 feet tall or more after several years.
