They are remarkable for the great size, length of tube, and beauty of their flowers, borne upon generally small and dumpy stems.

[1] It was concluded that previous taxonomic confusion was due to convergent evolution: species in different lineages had evolved to have similar growth and/or to share pollinators.

[4] As of December 2024[update], Plants of the World Online accepted Echinopsis more narrowly circumscribed to include only 20 species,[5] the others being separated in Acanthocalycium, Chamaecereus, Leucostele, Lobivia, Reicheocactus, Setiechinopsis, Soehrensia and Trichocereus, and in one case (E. cephalomacrostibas ) moved to Weberbauerocereus.

[5] They thrive in desert grasslands, shrubland, and in situations where the soil is sandy or gravelly, such as the sides of hills in the crevices of rocks.

[citation needed] Research by J. Smith (former Curator at the Royal Botanic Gardens, Kew) showed that species like the Chilean Echinopsis cristata and its Mexican relatives thrive if potted in light loam, with a little leaf mould and a few nodules of limestone.