Star cactus care guide
Astrophytum
Also known as: Sand dollar cactus, Bishop's cap, Astrophytum ornatum
Pets and children
We haven't been able to confirm how this plant affects pets or small children. If any is eaten, consult a veterinarian or a doctor.
How often to water Star cactus
- Spring–Summer (Mar–Sep)
- Every 10 days
- A summer grower that slows in the Japanese midsummer: water well a few days after the soil dries through, and sparingly in the evening in July and August, as a guide.
- Autumn (Oct–Nov)
- Every 14 days
- It grows again as it cools: water about one to two weeks after the soil dries, as a guide.
- Winter (Dec–Feb)
- Every month
- Dormant: close to dry, wetting just the surface about once a month on a warm morning, as a guide, and keep sand dollar cacti the driest.
Light and placement for Star cactus
A sunny, airy spot as a guide, but midsummer sun scorches the skin, so shade it or use bright partial shade from June to September; bishop's caps generally take more sun than sand dollar cacti, and low light stretches them tall.
Overwintering Star cactus
Overwintering guide: 5°C (41°F) or above
Kept dry it generally takes about 5°C: as a guide, move it to a bright window indoors when nights fall below 8°C and rest it dry, since cold and damp together rot the roots.
Fertilizing and repotting Star cactus
Fertilizer
Feed sparingly: diluted liquid fertilizer about once a month from April to September and none in fall or winter, as too much cracks the skin or spoils the shape.
When to repot
Spring–Summer (Mar–Sep)
Common problems with Star cactus
- Watered in winter, it rots and goes brown and soft from the base.
- Midsummer sun scorches the skin and leaves pale scars.
- Short of light it grows tall and loses its neat star shape.
Tips for growing Star cactus
- Watering only after the skin wrinkles slightly avoids most trouble.
- Water the soil, not the plant, so the white flecks stay clean.
- It grows slowly, so repot only every two or three years, in spring.
These are AI-generated general guidelines. They vary with the variety, the placement and the pot size. For effects on pets or children, consult a veterinarian or a doctor.
Keep your plant log going
Greenery is a free app that keeps your plant care going, with watering reminders and photo records. Available on iOS and Android.
