Mammillaria

Morphological Summary

Mammillaria is the largest genus in Cactaceae with more than 200 accepted species, distributed primarily in Mexico (where the vast majority of species occur) and secondarily in the southern United States, the Caribbean, and northern South America. They are distinguished from all other genera by their tuberculate (not ribbed) structure: tubercles are cone-cylindrical protuberances bearing apical areoles, while flowers and fruits emerge from axillary woolly or bristle-bearing zones between tubercles — a diagnostic character unique to this genus. Most species form globose to cylindrical plants, solitary or densely caespitose, of small size (5–20 cm), although some reach 40–50 cm. Flowers are typically small (1–3 cm) and form striking crowns or rings at the top of the plant; the floral palette encompasses pink, red, white, yellow, and purple. Fruits are elongated bright-red to pink or green berries that persist long on the plant. Numerous species exude milky latex when cut (section Hydrochylus). The genus was described by Haworth in 1812; the current classification (D.R. Hunt, CITES Cactaceae Checklist) recognizes more than 200 valid species.