Opuntia polyacantha aka Cliff Prickly Pear

Opuntia polyacantha is a perennial cactus called plains prickly pear. It belongs to the cactus family, Cactaceae. Its range spans southern Canada, much of the western United States, and northern Mexico. It grows on dry plains, sand hills, and rocky ground. It also occurs in scrub and open woods. Mammals eat its fruit and spread its seeds.

The plant forms low mats of flat, joined stems. RHS gives a garden height of 0.3–1.6 feet [0.1–0.5 metres]. Its listed spread is 4.9–8.2 feet [1.5–2.5 metres]. Virginia Tech describes clumps reaching 2 feet [0.6 metres] tall. The round or oval pads are green to grey-green. Woolly brown patches called areoles bear spines and tiny barbed glochids. These loose bristles lodge in skin and can cause pain. Spine length, shape, and colour vary across the species.

Flowers grow near the edges or tips of the pads. They may be yellow, pink, red, or magenta. Sources place flowering from late spring into summer. Chicago Botanic Garden lists a broader March-to-August bloom window. Flowers reach about 0.16–0.25 feet [0.05–0.075 metres] across. The barrel-shaped fruit ripens toward the end of summer. Virginia Tech describes fruit turning from yellow-green to purple. Fruit texture varies in the accounts: fleshy there, but dry in PFAF. Some fruits bear short spines.

Give this cactus full sun and soil that drains well. RHS lists sandy and loamy soils across a broad pH range. For glasshouse plants, let the compost dry between growing-season waterings. Keep dormant plants dry and stop feeding them in winter. Hardiness accounts differ sharply and need care when choosing a site. Chicago Botanic Garden lists USDA zones 3–8. RHS gives H1C and recommends growing under glass. The plant suits containers and specimen planting. It needs no pruning, but may take 10–20 years to mature. Scale insects and mealybugs can attack it. Wet soil can cause root rot.

PFAF records food uses for fruit, seeds, and young pads. People eat fruit fresh or dried and cook the pads. They roast and grind seeds for use with flour. These uses require removal of spines and barbed hairs. RHS flags skin and eye irritation in people and dogs. PFAF also records traditional remedies made from stems. Other uses include fruit dye, stem adhesive, and fixing dyes. These records describe past uses, not proof of medical benefit.