From the city name Copiapo in Chile.
Body solitary or in clusters that form into mounds; spherical to cylindrical, sometimes almost white, the apex often densely woolly felted. Root fibrous and woody to swollen and tuberous. Stems strongly to weakly ribbed and sometimes with tubercles. Spines present to almost absent. Flowers small, funnel- to bell-shaped, yellow (rarely red); summer. Pericarpel and flower tube naked or with a few scales. Fruit small, splitting at the narrowed tip which usually has 1-2 scales.
A difficult genus with many poorly defined species and needing revision.
Flowers mostly yellow and with a short tube; fruit splitting at the tip, the floral remnants often forming a lid.
Possibly 10-20 species from the coastal deserts of N Chile.
Source: (1997). Cactaceae. In: . 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.