Mammillaria hahniana is a popular sun-loving succulent that forms large groups. It is readily identified by its long, white, thin, flexible hairs which can densely cloak the plant's body and increase in thickness, richness and length in age. This cactus flowers prolifically, even when young, making it a good species to have in a collection. Includes numerous variations and described subspecies, none of which are currently accepted.
It is a rapid growing species that will form large clumps rather rapidly when compared to other Mammillaria species. Needs lots and lots of space to grow. Water regularly in summer, but do not overwater (Rot prone) Use pot with good drainage and a very porous potting media, keep dry in winter. Feed with a high potassium fertilizer in summer. It is quite frost resistant if kept dry, hardy as low as -5° C (some reports give it hardy to -12°C) Outside full sun or afternoon shade, inside needs bright light, and some direct sun.