Echinopsis arachnacantha, synonym Lobivia arachnacantha, is a species of cactus in the genus Echinopsis, native to Bolivia.
Description Echinopsis arachnacantha typically grows in clusters with flattened to spherical stems that are dark green and feature around 14 weakly notched ribs. The areoles on these stems bear 9-15 radial spines measuring 5 mm in length, which can range from pale to dark brown or yellowish-brown, sometimes accompanied by a 1.5 mm long black spine. Its flowers are approximately 5 cm wide and are supported by a slender floral tube that is about 5 cm long.
Taxonomy The species was first described in 1956 as Lobivia arachnacantha.
Subspecies , Plants of the World Online accepted the following subspecies: Image Subspecies Distribution Echinopsis arachnacantha var. arachnacantha Bolivia Echinopsis arachnacantha var. densiseta BoliviaEchinopsis arachnacantha var. sulphurea Bolivia Echinopsis arachnacantha var. torrecillasensis Bolivia
Distribution Plants are found in Bolivia, in the departments of Santa Cruz, Chuquisaca, and Cochabamba, as well as in Salta, Argentina. It grows at elevations between 1800 and 2600 meters. This species grows on stony hills in places with reliable summer rainfall.
Cultivation The species has gained the Royal Horticultural Society's Award of Garden Merit.
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