Astrophytum are small hemispherical cacti with a few prominent ribs and a thin layer of white, woolly scales. Bishop’s cap, sea urchin cactus, sand dollar, and goat’s horn cactus are various names given to different species of Astrophytum.
Astrophytum species diifer; some are completely spineless, others produce dense woolly hair..They produce single flowers–sometimes two or more grouped together–that open on successive days. The flowers are scented, yellow, or red and crown the cap of the plant. Astrophytumspecies usually grow to about 2 feet tall.
Get to Know Astrophytum
- Plant type: Cactus, star cactus
- Hardiness temperature: 25℉ (-4℃)
- Optimal growing temperature: day, 80° to 85°F (27° to 29°C); night, 62° to 65°F (17° to 18°C).
- Shape and size: Small, hemispherical cacti can grow to 2 feet tall or taller; completely spineless
- Flowers: Single, scented, yellow or red flowers appear singlely or in groups
- Bloom time: Summer and autumn
- Common name: Bishop’s cap, sea urchin cactus, sand dollar, and goat’s horn cactus
- Genus name: Astrophytum
- Family name: Cactaceae
- Origin: Texas, Mexico
- Most plants can withstand full sun, but partial shade is best during hottest months.
- Indoors bright, filtered sun from southern, southeastern, or eastern exposure. A. myriostigma prefers a semishady locale. Fresh air circulation is important.
- The soil should be sligthly acidic, sandy-humous soil, containing a little calcium sulfate, mixed with clay and pumice.
How to Water and Feed Astrophytum
- Water Astrophytyum sparesely and keep dry during the winter.
- Let soil dry between thorough waterings. Overwatering causes plant to rot.
- Humidity best at 30% to 35%.
- Feed Astrophytum every 6 weeks during growing season, with low-nitrogen, high-potassium fertilizer.
- Transplant Astrophytum only when necessary; the roots are very sensitive.
- Propagate Astrophytum by seed, offsets, or by grafting.
- Check for aphids, mealybugs, spider mites, scale. Also, be alert for fungus disease.
- Astrophytum rests from fall to early spring. Place the plant in a cool, bright location where it receives 5 hours of sunlight daily. Decrease water and withhold fertilizer.
Growing Astrophytum as a Houseplant
- Astrophytum requires direct light, low humidity, a warm temperature in summer and a cool temperature in winter.
- Allow the soil to dry thoroughly between waterings; excessive watering can cause raised, scablike tissue to appear on the cactus.
- Fertilizer should be applied during the cool-temperature, low-light months of late winter or early spring.
Astrophytum Species to Grow
- Astrophytum asterias (sea urchin cactus, sand dollar). Flattened globular body and spineless, prominent ribs; measures 2 inches (5 cm) tall, 3 inches (8 cm) wide; large, white, pimplelike areoles dot the gray green surface of the cactus; tufts of white on its body[ bears yellow flowers with contrasting scarlet throats.
- A. capricorne (goat’s horn cactus). Twisted almost distorted spines that curl to look like the horns of a goat’; globular body is white flecked; thin, wavy spines grow from depressed areoles along the crests of the ribs; flowers are yellow with scarlet centers.
- A. myriostigma (bishop’s cap). Swollen gray-green body broken by five prominent ribs, covered with fine white wool; no apparent spines; showy yellow flowers, 2 inches (5 cm) wide.
- A. ornatum (star cactus, ornamental monk’s Hood). Globular when young, columnar when mature; growing to 32 inches (81 cm) wide; heavily ribbed (usually with 8 ribs); bodies decorated with bands of white woolly hair; slightly curved spines are yellow but turn brown as plant ages; flowers in various shades of yellow. Variety ‘mirbelli’, has golden spines that are somewhat shorter, less attractive.