Echinopsis is a large genus of cacti native to South America, sometimes known as hedgehog cactus, sea-urchin cactus or Easter lily cactus. One small species, E. chamaecereus, is known as the peanut cactus. The 128 species range from large and treelike types to small globose cacti. The name derives from echinos hedgehog or sea urchin, and opsis appearance, a reference to these plants' dense coverings of spines. They are remarkable for the great size, length of tube, and beauty of their flowers, which, borne upon generally small and dumpy stems, appear much larger and more attractive than would be expected. Taxonomy Studies in the 1970s and 1980s resulted in several formerly separate genera being absorbed into Echinopsis: Some have proposed merging Rebutia as well. Like several other taxonomic changes in Cactaceae, this one has not been universally accepted. Amateur and professional growers still use names like Echinopsis (in the older sense), Lobivia, Setiechinopsis and Trichocereus, although many of the others listed above fell out of common usage long before the change. Changing the genus name necessitated using some different specific epithets to avoid creating duplicate names. Thus both Echinopsis bridgesii and Trichocereus bridgesii previously existed. These are very different plants: Echinopsis bridgesii is a short clumping cactus, whereas Trichocereus bridgesii is a tall columnar cactus similar to E. (or T.) pachanoi. Under the new classification, Trichocereus bridgesii becomes Echinopsis lageniformis. The genus name Trichocereus was given to a number of columnar cacti in 1909 by Vincenzo Riccobono, before the genus was subsumed—along with Lobivia—into Echinopsis in 1974 by Friedrich. A 2012 genetic and morphological study by Albesiano found Trichocereus to be monophyletic if it included three species of Harrisia. A 2012 genetic analysis of chloroplast DNA indicates Echinopsis is made up of several divergent lineages. E. spachiana was not included in the study but is thought to be related to a Helianthocereus clade. Soehrensia Backeb. was found to be a separate genus, with synonym Helianthocereus Backeb. Species Note: some of the species listed below may be synonyms, subspecies, or varieties of others. Echinopsis adolfofriedrichii G. Moser Echinopsis amoenissima Werdermann Echinopsis ancistrophora Spegazzini Echinopsis antezanae (Cárdenas) H. Friedrich & G. D. Rowley Echinopsis apiculata Linke Echinopsis arachnacantha (Buining & F. Ritter) H.Friedrich Echinopsis arebaloi Cárdenas Echinopsis atacamensis (Philippi) H. Friedrich & G.D. Rowley Echinopsis aurata Salm-Dyck Echinopsis aurea Britton & Rose Echinopsis backebergii Werdermann Echinopsis baldiana Spegazzini Echinopsis berlingii Y. Ito