Plants
Bishop's Cap Cactus
Astrophytum · Cactaceae
The bishop's cap is a small jewel among cacti: a globular to columnar body with usually five sharply drawn ribs that looks like a star when viewed from above. The best-known species, Astrophytum myriostigma, is completely spineless and covered instead in fine white woolly flecks. A classic for collectors, and an easy-going character plant on the windowsill for beginners.
- Light
- Very bright with direct sun; protect from concentrated midday sun behind window glass at midsummer.
- Watering
- Sparingly — in summer water only after the substrate has dried completely, not at all in winter.
- Care level
- Medium
- Botanical
- Astrophytum
The genus is small but varied: Astrophytum myriostigma is the classic spineless bishop's cap, Astrophytum asterias grows flat like a sea urchin, Astrophytum ornatum carries strong spines and grows largest, and Astrophytum capricorne stands out with twisted, papery spines. Among collectors, Japanese cultivars such as Super Kabuto with dense white flecking fetch astonishing prices.
What surprises many people: the bishop's cap flowers reliably as a houseplant. Even young plants open silky, glossy yellow blooms at the crown in summer, often with a red throat, lasting several days and reopening in the sun.
The white dots on the epidermis are not a disease but tiny tufts of woolly hair that protect the plant from harsh sun in its homeland. Spraying or wiping them off damages this natural sunscreen — the bishop's cap wants to be admired dry.
The typical beginner's mistake here, too, is watering by the calendar. Astrophytum has sensitive roots and rots quickly in wet, humus-rich substrate. Purely mineral substrate, thorough watering followed by complete drying, and a cold, bone-dry winter rest are the whole secret.
As a spineless species, Astrophytum myriostigma is incidentally one of the few cacti you can safely place within reach of children and pets — the genus is not poisonous.
Is Bishop's Cap Cactus toxic to children and pets?
- Children
- Non-toxic
- Cats
- Non-toxic
- Dogs
- Non-toxic
Astrophytum is considered non-toxic to cats, dogs and people. The spineless Astrophytum myriostigma also poses no injury risk; spined species such as Astrophytum ornatum can prick.
Overview: toxic & non-toxic plants for cats, dogs and children
Care
- 01A very bright spot with a few hours of sun; shade lightly from harsh midday sun behind glass at the height of summer.
- 02Plant in purely mineral substrate (pumice, lava, coarse sand) — no ordinary potting compost.
- 03From April to September water thoroughly, then let the substrate dry out completely.
- 04From October to March overwinter cool (5–12 °C) and completely dry — this encourages flowering.
- 05Feed weakly with cactus fertiliser only two or three times per season.
- 06Do not mist, and do not wipe off the white flecking.
Frequently asked
- Why does my bishop's cap cactus have no spines?
- That is completely normal: the classic bishop's cap Astrophytum myriostigma is naturally spineless. Instead of spines it protects itself from the sun with the fine white woolly flecks on its skin. Other species in the genus, such as Astrophytum ornatum, do carry strong spines.
- When does the bishop's cap cactus flower?
- From around May to September, often in several flushes. The yellow, silky flowers appear at the crown and open on sunny days. The prerequisite is a cool, dry winter rest — keep the cactus warm all year and you will usually wait for flowers in vain.
- Is the bishop's cap cactus toxic to cats or dogs?
- No, Astrophytum is considered non-toxic to cats, dogs and people. The spineless species is actually one of the most pet-friendly cacti of all, since there is no injury risk either.
- How fast does a bishop's cap cactus grow?
- Slowly — and that is exactly what makes it so easy to keep. A few centimetres of growth per year are normal, so large specimens are correspondingly many years old. Buying a stately plant means buying a piece of a nursery's patience along with it.