An easy species that will form large clumps with age. Mammillaria longimamma has a fairly large tap root, and should be kept in a deep pot with a very draining mineral substrate. Watering during the active growing season (spring and summer); this will encourage steady growth, and prevent the large tubercles from becoming flabby. But be careful with watering, which all thick rooted species require (rot sensitive). Keep dry during the winter rest, when the plant may pull near the surface of the potting mix.
Fertilize every 2 weeks with diluted high potassium fertilizer when the plant is in bud. Need light shade to shade.

Propagation: Seeds, offsets, tubercles (Tubercles can be removed from the plant, let to dry a day or 2, and planted)