Echinopsis

Echinopsis is a South American cactus genus of roughly 80 accepted species (Kew POWO) ranging from small globose forms to tall columnar pillars reaching 6 m. Botanist H. Friedrich merged the formerly separate genus Trichocereus into Echinopsis in 1974 on the basis of shared floral structure, making Trichocereus a synonym. The old name persists in the nursery trade because it predates the reclassification and remains recognizable to collectors.

Echinopsis species are native to a broad arc of South America spanning Ecuador, Peru, Bolivia, Argentina, Brazil, Paraguay, and Uruguay. The columnar species dominate Andean slopes at 1,000 to 3,000 m elevation, growing in semi-arid shrubland and rocky grassland. E. pachanoi is native to the Peruvian and Ecuadorian Andes at 2,000 to 3,000 m, while E. peruviana occupies lower, drier slopes at 1,000 to 2,500 m.

Echinopsis pachanoi adds 30 to 45 cm of height per year under good conditions, making it among the fastest-growing columnar cacti in cultivation. E. peruviana can push faster still, sometimes exceeding 50 cm per year in warm climates with adequate water. Both rates apply to plants in their second year and beyond; juveniles grow more slowly while establishing roots.

Echinopsis produces some of the largest flowers in the cactus family: funnel-shaped blooms up to 25 cm long borne on a hairy floral tube, in white, pink, red, or yellow depending on species. Most columnar species in the former Trichocereus group open at night and last a single day. Smaller globose species more often bloom during daylight.

Echinopsis pachanoi tolerates brief frosts to approximately −5 to −7°C when the root zone is kept dry, placing it in USDA zones 9a to 10. Its high-altitude Andean origin means it is adapted to cold nights paired with dry soils; wet-cold conditions are far more damaging than dry-cold at the same temperature.

E. pachanoi has light green stems, typically 5 to 8 ribs, and short spines usually under 2 cm; it is native to higher, moister Andean sites at 2,000 to 3,000 m. E. peruviana shows a noticeably blue-green stem, larger areoles with spines reaching 4 cm, and originates from drier, lower-elevation slopes at 1,000 to 2,500 m. Both hybridize freely in cultivation, meaning plants sold under either name may be intermediate.

E. pachanoi is legal to buy, sell, and grow in the United States, the United Kingdom, Canada, Australia, and most other jurisdictions when kept as an ornamental. The cactus does contain mescaline, a Schedule I controlled substance, but the plant itself is not scheduled; legal exposure arises only if the intent is to extract or consume mescaline.

Echinopsis performs best in a fast-draining mineral mix: standard cactus soil cut with 30 to 50% pumice, granite grit, or lava rock. Unlike many desert cacti, the columnar former-Trichocereus species originate in high-rainfall Andean environments and can handle generous watering during the growing season, provided the substrate drains completely within 24 hours.