Mammillaria mystax

Mammillaria mystax is a small cactus in the Cactaceae family. It comes from Mexico, with a range from Veracruz to Oaxaca. It grows in the highlands of southern central Mexico. Sites include Puebla and nearby parts of Guerrero and Oaxaca. Its habitats include dry scrub, oak woods, and dry deciduous forest. Most reported sites lie at 3,281–8,530 feet [1,000–2,600 metres]. It remains abundant within its range, though farming and ranching affect its habitat.

The plant starts with one round or short, upright stem. Older plants may produce offsets and form loose clumps. Stems reach 0.23–0.49 feet [0.07–0.15 metres] tall. Each stem measures about 0.23–0.33 feet [0.07–0.10 metres] across. The dark grey-green stem has a flat top. Firm, pyramid-shaped tubercles cover its surface in close rows. Each tubercle has four to six angles and sharp ridges. Cuts or punctures release a milky fluid. Wool and bristles grow in the gaps between tubercles.

Small radial spines spread out from each spine cluster. These white spines may have darker tips. Each cluster has three to ten radial spines. The thicker central spines twist and cross one another. They begin purple with dark brown tips, then turn grey. Their number varies, though four is usual. One may reach 0.23 feet [0.07 metres] long. Plants in cultivation do not always develop this long spine. In the wild, tangled spines can hide the crown.

Rose-purple flowers form rings near the top of the stem. They can crowd together in two or three rows. Brownish lines run along the flower segments. The inner segments are dark red, with greenish stigma lobes. Flowers measure 0.03–0.08 feet [0.01–0.025 metres] across. In its native habitat, flowering runs from February through April. Red, club-shaped fruit follows, with brown seeds inside. The fruit reaches about 0.08 feet [0.025 metres] long.

This species is widely grown for its spines and flowers. It is easy to grow in porous cactus compost. Excellent drainage is a key need. Protect it from frost, despite reported tolerance to 23°F [-5°C] when dry. Repot plants every two or three years. Seed provides a means of propagation; sow after the last frost. During active growth, use feed with more potassium and phosphorus than nitrogen.