Echinopsis

Echinopsis is a genus of cacti native to South America, sometimes known as hedgehog cactus, sea-urchin cactus or Easter lily cactus. , there are about 20 accepted species, ranging 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, borne upon generally small and dumpy stems.

Taxonomy
Studies in the 1970s and 1980s resulted in several formerly separate genera being absorbed into Echinopsis. When very broadly circumscribed, Echinopsis sensu lato included over 100 species. Some genera have been absorbed and then accepted again. For example, the genus name Trichocereus was given to a number of columnar cacti in 1909 by Vincenzo Riccobono. The genus was subsumed into Echinopsis in 1974 by Friedrich, along with Lobivia. In 2011, it was argued that Trichocereus was distinct from Echinopsis, and 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 indicated Echinopsis was made up of several divergent lineages. This was shown again in 2019.

, Plants of the World Online accepts Echinopsis more narrowly circumscribed to include only about 20 species, the others being separated in Acanthocalycium, Chamaecereus, Leucostele, Lobivia, Reicheocactus, Setiechinopsis, Soehrensia and Trichocereus, and in one case (E. cephalomacrostibas ) moved to Weberbauerocereus.

Species
Species of Echinopsis sensu stricto accepted by Plants of the World Online : Other species sometimes accepted in this genus are Echinopsis huotii and Echinopsis mieckleyi. In addition, many hybrids exist, mostly between similar species but also between more distinct ones, such as the cross between Trichocereus pachanoi (now Trichocereus macrogonus var. pachanoi) and E. eyriesii (now E. oxygona) which was sold under the name "Trichopsis pachaniesii" by Sacred Succulents.

Distribution
Echinopsis species are native to South America (Argentina, Bolivia, Peru, Brazil, Paraguay and Uruguay). 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.

Cultivation


The growing and resting seasons for Echinopsis are the same as for Echinocactus. 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. The limestone keeps the soil open; it is important that the soil should be well drained.