Opuntia robusta aka Wheel Cactus

Opuntia robusta is an evergreen cactus from Mexico. It belongs to the cactus family, Cactaceae. Its common names include wheel cactus and wheel pear. It grows in dry scrub, grassland, and pine and oak woods. People gather its fruit and pads from wild plants. They also grow it for food and manage wild stands. The species has a Least Concern conservation rating.

This cactus forms a shrub or a small tree. RHS gives a garden height and spread of 1.6–3.3 feet [0.5–1 metre]. In Mexico, plants reach about 6.6 feet [2 metres]. Useful Tropical Plants reports heights of 3.3–9.8 feet [1–3 metres], sometimes more. Thick, flat stem pads form its branches. The pads look round and have a grey or blue cast. They can reach 1.3 feet [0.4 metres] across. Each areole can bear two to twelve spines. Tiny barbed bristles, called glochids, add another handling hazard.

Mature plants bear yellow flowers in summer. The flowers have a shallow bowl shape. Round red fruit follows the blooms. RHS says UK-grown plants seldom flower or set fruit. Bees and other insects pollinate the flowers. The fruit has tart or mildly sweet flesh. People eat both fruit and stem pads raw or cooked. They also fry the fruit peel. Young pads reach local markets and are sold canned. Ripe fruit can stay edible on the plant for a year or more.

Give this cactus full sun and soil that drains well. RHS recommends sandy soil or cactus compost for pots. A loam-based mix with added sharp sand also suits it. Let the compost dry before watering during active growth. Stop watering and feeding during its winter rest. RHS rates it H1C for UK conditions. This means summer outdoor use, with winter shelter under glass. PFAF lists USDA zones 9–11. RHS recommends it for homes, conservatories, and greenhouses. Seeds and rooted stem sections provide ways to raise new plants.

The plant needs no routine pruning and has few disease problems. Scale insects and mealybugs may attack it. It can escape cultivation and grow as a weed. Its spines and glochids make handling difficult. The bristles can lodge in skin and cause pain. RHS warns of skin and eye irritation in people and dogs. Wear gloves and other protection when handling it.