About Echinopsis oxygona (Link) Zucc. ex Pfeiff. & Otto
Echinopsis oxygona (Link) Zucc. ex Pfeiff. & Otto can grow either alone or in groups. Its dark green shoots are spherical to short cylindrical, growing up to 75 cm (30 in) in height and up to 15 cm (5.9 in) in diameter. The cactus has 8 to 18 ribs, with areoles that range from white to tan, gray, or black, spaced up to 2 cm (0.79 in) apart. Spines emerging from the areoles vary in both size and number. For plants previously classified as E. eyriesii, there are 10–15 very short spines. For plants classified as E. oxygona, spines are longer: 1 to 5 strong central spines reach 3–3.5 cm (1.2–1.4 in) in length, and up to 20 thinner radial spines grow up to 2.5 cm (1.0 in) long. This species produces white, lavender, or pale red night-opening flowers that grow up to 25 cm (9.8 in) long and up to 10 cm (3.9 in) across. Echinopsis oxygona is native to Southern Brazil, Uruguay, Paraguay, and Entre Ríos Province, Argentina, where it grows in lowland environments up to 1,000 meters above sea level. Its native range has a tropical continental climate with arid winters and humid summers. Annual precipitation in these regions is approximately 1,500 mm, and the average annual temperature ranges from 25–30°C, rarely dropping below 0°C. In cultivation, Echinopsis oxygona is recognized for its large, showy flowers that grow at the ends of long tubes connected to the cactus. The flowers have a sweet scent, open in the evening, and wilt by the following afternoon on hot days. It grows well in full sun or light shade, tolerates high heat, and can survive temperatures as low as −10 °C (14 °F). It is typically grown as an outdoor plant. Adapted to dry, desert-like conditions, it does not require daily watering. In the 19th century, Echinopsis oxygona was widely hybridized with other Echinopsis and Lobivia species, producing many cultivars with large colourful flowers. When grown in cultivation in the United Kingdom, this plant has earned the Royal Horticultural Society's Award of Garden Merit.
