Rauhocereus

Rauhocereus is a monotypic genus of cacti (family Cactaceae). Its only species is Rauhocereus riosaniensis, which has nocturnal flowers. It is known from northern Peru (Rio Santa, Rio Zana, Chamaya and Jaén).

Description
The mostly shrubby Rauhocereus riosaniensis, usually branching from the ground, often forms thickets up to 4 meters high. The upright, columnar shoots are bluish-green and have a diameter of 8 to 15 cm. The 5 to 6 ribs are broken up into many warts. 2 to 8 strong spines, up to 5 cm long, emerge from the woolly areoles. The lower ones are initially reddish, the upper ones yellowish. Later all become greyish-white.

The bell-shaped flowers appear near the shoot tip. They open at night, are 8 to 10 cm long and have a diameter of up to 5 cm. The flower cup and the flower tube are covered with small scales and curly brown hairs.

The red, fleshy fruits are ovoid with a persistent flower rest. They contain small, ovoid, shiny black seeds.

Taxonomy
The genus and its only species were first described in 1957 by Curt Backeberg. , Plants of the World Online accepted two subspecies:
 * Rauhocereus riosaniensis subsp. jaenensis (Rauh) Ostolaza
 * Rauhocereus riosaniensis subsp. riosaniensis

Distribution
Rauhocereus riosaniensis is found in northern Peru in the Amazonas and Cajamarca regions at altitudes of 500 to 1000 meters.