About the Old Man Cactus

Species

• This cactus also is known by its scientific name, Cephalocereus senilis. This species name roughly translates from Latin as "waxen-headed old man." Its common name also derives from the long white hairs that grow on the cactus, giving it a shaggy, bearded appearance. These hairs protect the cactus from the sun and conceal its sharp yellow thorns.

Genus

• The old man cactus belongs to the Cephalocereus genus, or "waxen-headed" cactuses. According to ZipCodeZoo, this genus contains about 120 species, including the pipe organ cactus of the Caribbean and the Yucatan Peninsula in Mexico. Cacti in this genus tend to grow slowly and have a bluish green, columnar and hairy appearance. Some members of this genus once were categorized as Pilocereus.

Tribe

• Cephalocereus senilis is a member of the Pachycereeae, a tribe containing about 15 genera of North American columnar cacti. These cacti are native to Mexico, Central America, the Caribbean and the southwestern United States. In addition to the old man cactus, this tribe also contains the more familiar saguaro and snake cacti.

Family

• Like all cacti, the old man cactus belongs to the Cactaceae, or cactus family. These plants are fleshy, with leaves that evolve into spines and stems containing large amounts of moisture. Cacti are native only to the Americas, and grow from southern Canada south to Patagonia. Most cacti are found in northern Mexico and parts of South America. One species, Rhipsalis baccifera, is native to tropical Africa. This family contains 110 genera and more than 1,000 species. Nearly all cacti are succulents and are adapted to hot, dry environments.