Family: Cactaceae
Common Name: Crown Cactus

There are more than 40 species in this genus of cactuses from Bolivia and Argentina, all small and cluster forming. They have low, rounded tubercles and hairy, needle-like spines. The sometimes self-fertile flowers emerge from the base of the tubercles in late spring to early summer, and may be vivid orange, pink, purple, red or yellow, and sometimes white. They last up to several days and are followed by fleshy fruits, becoming papery with age. Plants regularly produce offsets.

Species

R. albiflora is composed of tiny plants with soft, white spines which grow very quickly to fill their pot. It has white flowers with a pink stripe down the middle of the petals. This species is self-sterile but flowers profusely.

R. aureiflora has clusters of deep green-purple bodies, covered in short, bristly, brown to gray spines. An abundance of golden-orange flowers, to 4 cm (1½ in) across, appears at the end of spring, from around the base of the plant.

R. kupperana has a purplish green body, with stiff, (lark brown spines, and deep red flowers, 4 cm (1½ in) in diameter.

R. minuscula is a dark green cactus, depressed at the apex, with spiralled tubercles and weak, yellow spines. The 2 cm (3/a in) flowers are crimson.

R. senilis, fire-crown cactus, is a fiat, bristly cactus with white spines and crimson flowers, to 4 cm (1½ in). Var. kesselringiana produces green buds, followed by yellow flowers.

Cultivation

In frost-prone climates, grow in an intermediate greenhouse or conservatory in pots of proprietary cactus compost. Provide full light and a dry, airy atmosphere. Do not water in winter but water in moderation during the rest of the year. Propagate in spring from seed germinated at 21°C (70°F), or in spring from offsets .

Climate

Zone 10 and above.