Old lady cactus (Mammillaria hahniana) is a flowering cactus in the family Cactacee. Old lady cactus is native to central Mexico. This species is considered to be nearly threatened in some areas and is listed on the IUCN Red List of threatened species. In order to grow in temperate regions, old lady cactus must be grown under glass with heat. It should be kept dry in the winter, and watered during its active growth cycle in the summer.