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 . The 5 to 6 ribs are broken up into many warts. 2 to 8 strong spines, up to 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 long and have a diameter of up to . 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==