About Acanthocalycium rhodotrichum subsp. rhodotrichum
Acanthocalycium rhodotrichum subsp. rhodotrichum typically grows in clusters, producing erect or ascending, cylindrical, dull green shoots. These shoots reach 30 to 80 cm (12 to 31 in) in height, and can grow up to 12 cm (4.7 in) in diameter. The cactus has 8 to 18 low, somewhat wavy ribs, with areoles spaced 1.5 to 2.5 cm (0.59 to 0.98 in) apart. Yellowish spines with brown tips grow from these areoles. One slightly upward-curving central spine, up to 2 cm (0.79 in) long, is usually present, but may sometimes be absent. There are also 4 to 8 spreading, slightly curved radial spines, each up to 2 cm (0.79 in) long. It produces funnel-shaped white flowers that open at night, and can reach up to 15 cm (5.9 in) long. This subspecies is widespread in the Brazilian state of Mato Grosso do Sul, Paraguay, and northeast Argentina, where it grows at altitudes up to 500 meters.
