Etymology -From the Greek -"OROS" meaning Mountain and the Latin "Cereus" meaning candle -hence Mountain cereus or Mountain candle .Oreocereus could possibly be considered the South American counterpart to that of Cephalocereus in the Northern Hemisphere. They are similar in that they are predominently short-columnar species which are covered in thick white wool or hair. Some species in this genus have so much hair that it completely obscures the stems underneath. While the wooly covering gives them a soft apperance, closer examination reveals sharp spines extending beyond the wool.
A number of Oreocereus species are found in cultivation, grown primarily for the dramatic white hairy stems and puts them all under the common name "Old Man Cactus" or "Old Woman Cactus". Stems underneath are ribbed and notched between areoles.
Flowers are not uncommon even in cultivation and are usually bright red or orange and quite striking. Flowers are bilaterally symmetrical and similar to that of the genus Cleistocactus under which at least once species was previously placed. The style and stamens protrude beyond the pericarples. Fruits are rounded and fleshy.
This genus is found at higher elevations - typically 10,000 feet or more in Peru, Chile, Bolivia, and Argentina. The white wool covering, no doubt provides protection against the intense UV at these elevations.