Parodia erinacea aka Parodia Erinaceus

Parodia erinacea is a small cactus in the Cactaceae family. The RHS calls it Colombian ball cactus. Its recorded native range covers Argentina, Uruguay, and southern Brazil. In Brazil, it grows in Rio Grande do Sul. It lives among rocks in grasslands and pampas. LLIFLE records it at elevations up to 98 feet [30 metres]. Older names include Notocactus erinaceus and Wigginsia erinacea.

Each plant has one stem, rather than a cluster. The stem ranges from pale green to deep green. It starts as a flattened ball or a rounded globe. With age, it may become a short cylinder. Reported height reaches about 0.49 feet [0.15 metres], sometimes 0.66 feet [0.20 metres]. Width ranges from 0.20 to 0.98 feet [0.06–0.30 metres]. Older plants grow a thick woolly cap called a pseudocephalium. Young plants can look quite unlike these woolly adults.

The ribs may slant or follow a wavy line. Young stems have 12–15 ribs; older stems may have 23–30. Crosswise grooves become more marked as the plant ages. The areoles sit in hollows along the ribs. Young areoles carry tufts of off-white wool. The pointed spines may be straight or curved. Their colours include white, yellow, grey, and brown. Each areole has two to twelve radial spines, most often eight. A central spine may be absent or point upward.

Summer flowers rise from the wool at the stem tip. They appear alone or in groups of two or three. Each bloom spreads wide, with glossy yellow inner tepals. Flowers measure 0.13–0.23 feet [0.04–0.07 metres] across. The outer tepals have red edges and dark, curved tips. Bright red stigma lobes stand out against the yellow flower. Dark wool and narrow green scales cover the short flower tube. The flowers open late in the morning.

The club-shaped fruit starts green and stays hidden within the wool. At first, it holds sticky pulp. It lengthens and turns pink or red as it ripens. Mature fruit becomes dry and hollow, holding about 70–150 seeds. The small, bell-shaped seeds range from light brown to black. The species remains abundant in some places and occurs in protected areas. Yet some populations in Brazil and Uruguay have disappeared. Grazing and forestry remain threats; illegal collecting could add pressure.