Mammillaria parkinsonii aka Owl's Eye

Mammillaria parkinsonii is a small cactus. Its common name is owl's-eye pincushion. It belongs to the cactus family, Cactaceae. It comes from Mexico, from Guanajuato to Veracruz. It grows in dry scrub and semi-desert on lime-rich ground. People who collect it by breaking the law threaten wild groups. Changes in land use pose a threat too. Growers raise it for show, often from stock they have bred or grown.

The plant starts with one round, blue-green stem. With age, its heads can split in two and form clumps. Each stem grows about 0.5 feet (0.15 metres) tall and wide. RHS gives a wider range for plants in gardens. Both height and spread reach 0.3–1.6 feet (0.1–0.5 metres). LLIFLE lists old clumps 2 feet (0.6 metres) across or more. White wool fills the shallow dip at each stem tip. Raised bumps, called tubercles, form spirals around the stem. Young areoles, the spots that bear spines, have white felt. This wears away with age. Each bears many fine white radial spines. The longer central spines curve down and have dark tips. New central spines may have purple-red tones.

Flowers open by day in rings near the tips. White wool surrounds the buds before they open. The blooms have a funnel shape and pale yellow petals. Their midstripes are pink or brown. Chicago Botanic Garden lists blooms from March through June. Small fruits shaped like clubs turn orange-red to scarlet. The brown seeds have a pear-like shape. LLIFLE lists the seeds as safe to eat. The supplied sources do not show that the whole plant is safe.

This cactus suits pots and displays in a greenhouse. It also suits small plantings as a specimen. Chicago Botanic Garden advises full sun and dry conditions. RHS advises bright, filtered light for growth under glass. Use cactus compost that drains well and keep air moisture low. Sandy or loamy mixes suit it across a broad pH range. Give modest amounts of water during growth. Then keep it almost dry through winter. RHS advises liquid feed every two to three weeks during growth. Its H2 rating means it needs shelter from freezing. Chicago Botanic Garden lists USDA zones 9–11. LLIFLE reports that dry plants can endure −5°C for brief spells. It still advises keeping them free from frost.

RHS says plants reach full size in five to ten years. Plants need no pruning. Growers can raise more from seeds or offsets. Sow seeds in early spring at 19–24°C. Mealybugs may attack the plant, so check for them. RHS reports few disease problems when growing conditions suit it.