Oreocereus is a genus of cacti (family Cactaceae), known only from high altitudes of the Andes.Its name means "mountain cereus", formed from the Greek prefix (Greek, Ancient (to 1453);: ὀρεο-, mountain) and the Neo-Latin Latin: cereus, meaning wax or torch.
The species of the genus Oreocereus grow shrubby, branching only sparsely from the base and reach heights of growth of 2 to 3 meters. Trunks are rarely formed. The erect, pendulous or rarely extended cylindrical shoots are notched or warty between the ribs. The areoles often have long white hairs and dense spines. As they are covered with woolly white fuzz (modified spines), a few species in this genus are sometimes known as the old-man cactus,[1] [2] a generic name that also refers to Cephalocereus senilis or Espostoa lanata. More rarely, the old man of the mountain is also used for some species.
The tubular to funnel-shaped, more or less radially symmetrical, orange to red to violet flowers arise near the shoot tip, or sometimes from the terminal cephalium, and open during the day. The flower-tube is straight to slightly curved and sometimes laterally compressed. The numerous areoles on the pericarpel and the flower tube are hairy. The spherical to oblong fruits contain broadly oval, dull or shiny black seeds.[3] [4]
, Plants of the World Online accepts the following species:[5]
| Image | Scientific name | Distribution |
|---|---|---|
| Oreocereus celsianus | Peru, Bolivia, Argentina (Jujuy) | |
| Oreocereus doelzianus | Peru. | |
| Oreocereus hempelianus | Peru to Chile (Tarapacá) | |
| Oreocereus leucotrichus | Chile, Peru | |
| Oreocereus pseudofossulatus | Bolivia. | |
| Oreocereus ritteri | Peru | |
| Oreocereus tacnaensis | Peru | |
| Oreocereus trollii | Argentina, Bolivia | |