Say it: ass-troh-FY-tum meer-ee-oh-STIG-muh. Common names: Bishop's Cap, Bishop's Hat, star cactus.
Where it grows
Limestone hills of central and northern Mexico, across Tamaulipas, Nuevo León, San Luis Potosí and Coahuila. The name myriostigma means “many dots,” for the white flecks covering the body.
Size and growth
A spineless body with 3 to 8 sharp ribs, most often five, giving a star shape from above. Starts globular and slowly becomes columnar, reaching 8 inches or more across and taller with age. Moderate growth: a seedling can be an inch across in a year or two and flowering size in 3–5 years.
Flowers
Glossy yellow flowers, about 2 inches across, from the crown in late spring and summer, repeating through the warm season. Plants flower young and often.
Care
- Light: bright light to full sun; the flecks are its sunscreen.
- Water: when dry in the growing season, sparingly or not at all in winter.
- Soil: gritty mineral mix with a little organic matter.
- Cold: handles brief dips to around 20°F if bone dry.
From seed
One of the easiest. Germination in 7–21 days at 75–85°F. Seed from variegated or nudum (fleck-free) parents gives a share of seedlings with those traits.
Bishop's Cap seeds · Nudum variegata seeds · Nudum seedling · Astrophytum cultivar guide