Stenocactus multicostatus aka Brain Cactus

Stenocactus multicostatus is a small cactus in the Cactaceae family. Its common names include wave cactus and brain cactus. It comes from Mexico, with a range reaching northern Jalisco. LLIFLE records it in Coahuila, Chihuahua and Durango. It grows in high, dry grasslands with rocky soil. During drought, plants may retreat into the ground. Kew also places it in desert and dry shrubland habitats.

Plants may grow alone or form small groups of stems. RHS gives a garden height and spread of 0.33 feet [0.1 metres]. Plants take about five to ten years to reach maturity. LLIFLE records stems up to 0.39 feet [0.12 metres] tall. Its wider plants reach 0.49 feet [0.15 metres] across. Stems range from flattened balls to short cylinders. Their colour varies from grey-green to deep green. The top of each stem is flat. Thin, close-set ribs give the surface its folded look. LLIFLE gives 50–100 ribs, with some plants exceeding 150. RHS describes plants with at least 100 ribs.

Young areoles carry a coat of white felt. Each rib has just a few of these spine-bearing points. Spine shape, length and colour vary among plants. RHS describes yellow or grey spines. LLIFLE also records cream to copper-brown central spines. Some upper spines are broad and flat; lower ones point down. Flowers open at the crown, above the ribbed stem. RHS describes pink, funnel-shaped blooms with a darker stripe on each petal. LLIFLE records white, violet and pink-purple flowers, with rare yellowish blooms. Flowers measure about 0.08 feet [0.025 metres] across. Spring is the main bloom season; LLIFLE also lists summer.

Grow this cactus in full sun with low air humidity. RHS recommends standard cactus compost with good drainage. It accepts sandy or loamy soil across a broad pH range. Water moderately while the plant grows, but keep it dry in winter. Apply a low-nitrogen feed each month during active growth. RHS rates its cold tolerance as H2. It tolerates cool conditions but cannot survive freezing. A sheltered, south-facing or west-facing spot suits its light needs.

RHS lists it for homes, conservatories, greenhouses and subtropical planting. Its small size suits pot culture in these settings. The folded stems and spring flowers provide its main visual interest. Grow new plants from seed; pruning is not needed. Watch for mealybugs, which can infest this cactus. Too much water can cause both root and stem rot.