Autor: Britton & Rose

Native of the mining region of La Oroya, in Peru, which gives its name to the genus.
A genus of low, subglobose flattened plants, with the apex depressed, sometimes becoming elongated with age, usually solitary, sometimes in groups, with tuberous roots, with epidermis fresh green to olive-green. Ribs numerous (24-30), areoles narrow and elongated, spines (16-24), interlaced, pectinate, stiff; usually no central spine.
Flowers diurnal, self-sterile, subapical, funnel-shaped to bell-shaped, with short floral tube slightly woolly and having small scales, with outer petals curved, yellow to greenish yellow or pink to red with an intense yellow heart, pollinated by hummingbirds, bees, butterflies (Hesperiidae) and possibly ants. Fruits more or less globose to davate, slightly fleshy, greenish pale or yellow pink, floral remains persistent. Seeds helmet-shaped, not wrinkled, foveolate or reticulate, reddish brown to black.
The genus Oroya has only and supposedly two extremely variable species, and grows endemically in the high valleys of the Peruvian Andes, in full sun, at ground level, among rocks and grasses (Stipa ichu) and lichens, on more or less rocky, gravelly or loamy clastic soils, from 2600 m up to 4300 m in altitude, sometimes together with other cacti. Plants can withstand frost and are often covered with snow in winter.
Peru (Ancash, Apurimac, Ayacucho, Cuzco, Huancavelica, Junin, Lima).

Currently 2 recognised species, but few others are possible:
– Oroya borchersii* (Boed.) Backeb. 1959
– Oroya peruviana* (K.Schum.) Britton & Rose 1922

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