Gymnocalycium andreae

Gymnocalycium andreae is a small cactus from Argentina. It belongs to the cactus family, Cactaceae. Kew records its native range as Córdoba. LLIFLE also lists San Luis. It grows high in the Sierras Grandes of Córdoba. Sites lie at 4,920–6,560 feet [1,500–2,000 metres] above sea level. Plants root in rock cracks or humus among grasses. Rain and mist bring moisture through the year. Snow falls there in winter.

Wild plants tend to grow alone, close to the ground. In pots, stems branch at the base to form clumps. RHS gives a mature height and spread of 0.33 feet [0.1 metres]. LLIFLE reports wider clumps reaching 0.49 feet [0.15 metres] or more. RHS gives five to ten years to reach full size. The plant has large taproots and squat, rounded stems. Each stem can reach 0.16 feet [0.05 metres] across. Its dark green skin may show blue or bronze tones. The top often dips inward. Eight to thirteen ribs bear rounded tubercles with deep cross-grooves.

Pale radial spines spread out from the tubercles. Their bases may have a chestnut tint. One to three dark brown central spines may curve upward. These slender spines have a rough surface. Bright yellow flowers open in early summer. Their shape ranges from a bell to a funnel. RHS gives a flower width of 0.13 feet [0.04 metres]. LLIFLE records blooms up to 0.18 feet [0.055 metres] wide. The flowers have little or no tube. Blue-green fruits follow, with round to cylindrical shapes. They measure about 0.04 feet [0.012 metres] across. The seeds are black and dull.

Grow this cactus in full sun with shelter. RHS suggests a south-facing or west-facing site. Use peat-free cactus compost, or loam-based compost with extra grit. Good drainage matters, and acidic to alkaline soils suit it. Water well during active growth, from March through September. Keep the compost dry through winter. RHS rates the species H2, so it cannot survive freezing. Its mountain habitat does not establish frost safety in cultivation.

RHS lists this cactus for patio pots and other containers. Its low clumps and yellow flowers provide its ornamental interest. It needs no pruning. Mealybugs may attack, though RHS reports few disease problems. Raise seeds in late winter or early spring under warmth. Spring is also the time to detach and pot offsets.