Family: Cactaceae
Common Name: Star Cactus, Bishop's Cap

These popular cactuses, originally from Mexico, vary in size and form, from globular to elongated to star-shaped. They are hard-skinned and divided into prominent ribs, and are covered with tufts of short hair which appear as small white spots. The spines, when present, are strong or papery and the yellow, diurnal, summer flowers are quite short.

Species

A. asterias, sea urchin cactus, does resemble a sea urchin. This highly valued species has a globular body divided into broad, vertical ribs, each with a row of small white areoles. It has no spines. The body is grayish green and the flowers are large and yellow with a red center. It prefers half-shade and less water than the others.

A. capricorne is a larger plant with high, rounded ribs, flat, twisted spines which grow to 70 mm (3 in) long, and large yellow flowers with red centers. The white tufts are sometimes almost absent and at other times quite dense.

A. myriostigma, bishop's cap, the most common of the species, is quite unusual looking. It has a globular body, with five to eight ribs and very dense tufts. It, too, is spineless. The glossy yellow summer blooms are smaller than those of the other species.

A. ornatum is a larger plant, with eight sharp ribs and sometimes hands of tufts. This species has straight, sharp, amber spines and pure yellow flowers.

Cultivation

Except in favorable Climates, they are grown in pots in a cool greenhouse, using a proprietary cactus compost. Provide bright light but shade from strongest sun. Keep dry in the dormant season. Outdoors, they need full sunlight, lots of water in spring and summer, and protection from rain in winter. Otherwise, they are easy to grow and frost-resistant.

Climate

Zone 9 and above.