About Mammillaria hahniana Werderm.
Mammillaria hahniana, commonly known as the old lady cactus, is a species of flowering cactus in the family Cactaceae that is native to central Mexico. This species grows up to 25 cm (10 inches) tall and can reach 50 cm (20 inches) across. It produces solitary spherical stems that measure 12 cm in diameter, and these stems are covered in white downy fuzz and white spines. Reddish purple flowers grow on the plant in spring and summer, and they sometimes form a complete ring around the apex, or top, of the cactus. The IUCN Red List lists the conservation status of Mammillaria hahniana as Near Threatened. Mammillaria hahniana is one of multiple Mammillaria species that are grown in cultivation. In temperate climate regions, it must be grown under glass with supplemental heat. Some cactus growers have reported that this species can tolerate temperatures as low as −5 °C (23 °F), and even as low as −10 °C (14 °F). Like all cacti, it needs to be kept completely dry during winter, and given water and fertilizer during its active summer growth period. It grows easily, starts flowering at a relatively young age, and is well-suited for cultivation in home gardens and collections. It has been awarded the Royal Horticultural Society's Award of Garden Merit.
