Body in groups with compressed or rounded bodies. Tubercles forming about 15-20 spirals. Areoles rounded. Spines 25-30, bristly, 2-3 mm long. Flowers of variable colour. Pericarpel pale red, the scales without bristles or hairs.

N Argentina

 

The similar R. senilis Backeb. has spines 2.5-3 cm long and flowers that are magenta with a white throat; f. kesselringiana (Bewer.) Buining & Donald has flowers that are yellow with a white throat. R. krainziana Kesselr. from N Argentina has a solid flower tube at the base and flowers red with a violet sheen and yellow throat. Plant possibly of garden origin.

Source: Thompson, A, ; Forbes, S.; Spencer, R. (1997). Cactaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.