Mammillaria spinosissima aka Spiny Pincushion Cactus

Mammillaria spinosissima is a cactus from Mexico. It belongs to the Cactaceae family. Its home range runs from Durango to Morelos and Guerrero. Gardeners call it the red-headed pincushion cactus. It grows in dry scrub and tropical dry forests. Wild plants grow at 5,250–6,230 feet [1,600–1,900 metres] above sea level. This succulent stays green all year.

The stems grow upright as short, narrow columns. Most plants have one stem. New shoots, called offsets, can grow at the base. Stems reach about 1 foot [0.3 metres] tall. Larger plants can reach 1.6 feet [0.5 metres]. Each stem grows up to 0.33 feet [0.1 metres] wide. Thick spines almost hide the dark blue-green stem. The spines at the centre may be red-brown or pink-brown. They may also be yellowish or white. Shorter spines, called radial spines, grow around them. These range from pale to brown. Their thin, needle-like shape varies from plant to plant. With good growing conditions, offsets can fill a pot within a few years.

Pink to purple flowers form a ring near the stem tip. The flowers reach about 0.07 feet [0.02 metres] long. Chicago Botanic Garden gives March to April as the bloom season. Insects seek nectar in the flowers and help pollinate them. The plant can also use its own pollen to set seed. Bright red fruit forms in fall and draws small birds. Birds whose beaks are long enough reach between the spines. The seeds are reddish-brown.

Grow this cactus in a bright spot with good drainage. Sources allow full sun or part shade. Under glass, bright light through a filter also suits it. Use a porous cactus mix with little organic matter. Give modest amounts of water while it grows. Then keep it almost dry in winter. Greenhouse plants do well when the air holds little moisture. RHS lists H2 hardiness. Chicago gives USDA zones 10–11. LLIFLE says dry plants can cope with some frost. Its claims about the lowest safe temperature differ. A sheltered, frost-free spot thus remains the safer choice.

This species suits pots and patio displays. It also suits plant collections grown under glass. In suitable climates, it serves as a border specimen. Its spines, spring blooms, and bird visits add garden interest. RHS reports few diseases, but mealybugs may attack. LLIFLE says poor drainage can lead to rot. Use a pot with drainage holes. Avoid pots that are too large. Repot every two or three years. The plant needs no pruning. Grow new plants from seed or offsets.