Autor: (Berger) Riccobono

≪Mountain cereus≫, referring to the preferred habitat of the genus.
A genus of ascending to erect, columnar, bushy to shrubby plants, branching from the base, reaching up to 3 m high, more or less covered with white setose hairs and spines according to species. Numerous ribs (10-25), rounded, tuberculate, areoles wide, woolly and strongly spiny. Central spines sturdy.
Flowers diurnal, self-sterile (some species are self-fertile), appearing below the apex (or at the apex in Morawetzia), more or less zygomorphic, tubular to funnel-shaped, orange, pink purple to more or less carmine red, or purplish brown, pollinated mainly by hummingbirds (Oreotrochilus estella, Patagona gigas) (or other birds (Sicalis raimondii), but also and occasionally, by bees, wasps and butterflies. Fruits globose to egg-shaped, elongated or pear-shaped, almost smooth, yellow, slightly aqueous, hollow, fleshy, dehiscence by a basal pore, soon falling, floral remains
persistent. Seeds black, roughly ovate, ruminate or foveolate, mostly matt, sometimes shiny (eg. Morawetzia).
The genus Oreocereus has a wide geographic distribution area, in the high mountains of the Andes, on high-plateaus, and grows mostly in full sun, on steep grounds between rocks, among grasses and bushes, from 1300 m up to 4250 m in altitude (O. trollii), often in huge colonies dominating the landscape.
Argentina (Jujuy, Salta), Bolivia (Chuquisaca, La Paz, Potosi, Tarija), Chile (Antofagasta, Arica, Tarapaca), Peru (Arequipa, Ayacucho, Huancavelica, Moquegua, Tacna).

Currently 8 recognised species (incl. a doubtful one, O. tacnaensis) + 2 subspecies:
– Oreocereus celsianus* (Lem.) Riccob. 1909
– Oreocereus doelzianus* (Backeb.) Borg 1937
– Oreocereus doelzianus subsp. calvus (Rauh & Backeb.) Mottram 2002
– Oreocereus doelzianus subsp. sericatus (Ritter) Mottram 2002
– Oreocereus hempelianus* (Gurke) D.R.Hunt 1987 (= Arequipa hempeliona, A. rettigii)
– Oreocereus leucotrichus* (Phil.) Wagenknecht 1956 (= O. hendriksenianus)
– Oreocereus pseudofossulatus D.R.Hunt 1991 (= o. fossulatus)
– Oreocereus ritteri Cullman 1958
– Oreocereus tacnaensis* F.Ritter 1981 ? (doubtful, poss. hybr.)
– Oreocereus trollii* (Kupper) Backeb. 1935

References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3692-8 (Vol. 2)