Astrophytum myriostigma
Astrophytum myriostigma
Astrophytum myriostigma, commonly known as the Bishop's Cap cactus, is a unique and striking succulent native to Mexico. With its distinctive star-shaped form and minimal care requirements, it is a favorite among collectors and beginners alike.
Everything it needs
9 essentials at a glance
Watering
Astrophytum myriostigma requires infrequent watering, typically every 2-4 weeks during the growing season (spring and summer).
Water thoroughly until it drains from the bottom of the pot, but ensure the soil dries out completely between waterings. In fall and winter, reduce watering to once every 4-6 weeks. Signs of over-watering include yellowing or mushy stems, while under-watering may cause shriveling or a wrinkled appearance.
Light
This cactus thrives in full sun, ideally receiving 6-8 hours of direct sunlight daily.
A south-facing window or a bright greenhouse is perfect for placement. While it can tolerate some partial shade, too much can lead to etiolation, where the plant stretches towards the light. Ensure it receives adequate light to maintain its compact shape.
Soil
Astrophytum myriostigma prefers well-draining soil with a pH range of 6.0 to 7.0.
A cactus mix or a blend of potting soil, sand, and perlite (1:1:1 ratio) is recommended to ensure proper drainage. Avoid heavy soils that retain moisture, as this can lead to root rot.
Humidity
This cactus prefers low humidity levels, ideally around 30-50%.
To increase humidity, you can place a humidity tray with water near the plant, but avoid direct contact with the water. Signs of humidity stress include browning or shriveling of the plant, indicating it may need more moisture in the air.
Temperature
Astrophytum myriostigma thrives in temperatures between 70-100°F (21-38°C) during the day and can tolerate cooler nights down to 50°F (10°C).
It is hardy in USDA zones 10-11. Protect it from frost and extreme cold, as prolonged exposure to temperatures below 30°F (-1°C) can be detrimental.
Fertilizing
Use a diluted cactus fertilizer with an NPK ratio of 10-10-10 or similar during the growing season, applying every 4-6 weeks.
In fall and winter, refrain from fertilizing as the plant enters dormancy. Signs of nutrient deficiency include slow growth and pale coloration.
Pruning
Astrophytum myriostigma generally does not require pruning, but any dead or damaged parts can be removed to maintain its appearance.
Use clean, sharp scissors or pruning shears to make cuts. Deadheading is not necessary for this cactus.
Repotting
Repot every 2-3 years or when the plant outgrows its pot, indicated by roots growing out of the drainage holes.
Choose a pot that is 1-2 inches larger in diameter. Carefully remove the plant from its pot, shake off excess soil, and place it in fresh cactus mix. Water lightly after repotting to avoid root rot.
Propagation
Propagation can be achieved through seeds or offsets.
For seeds, sow them in a well-draining cactus mix, lightly covering them, and keep them warm and moist until germination occurs in 2-4 weeks. Offsets can be carefully removed from the parent plant and allowed to dry for a few days before planting in a suitable mix. Best timing for propagation is in spring.
When it's unhappy
Yellowing stems
Why it happens
Over-watering or poor drainage.
How to fix it
Allow the soil to dry out completely before watering again, and ensure the pot has adequate drainage holes.
Wrinkled appearance
Why it happens
Under-watering or insufficient light.
How to fix it
Increase watering frequency and ensure the plant receives adequate sunlight.
Root rot
Why it happens
Excess moisture in the soil.
How to fix it
Remove the plant from its pot, trim away any rotted roots, and repot in dry, well-draining soil.
Etiolation
Why it happens
Insufficient light.
How to fix it
Move the plant to a brighter location to encourage compact growth.
Pest infestation (mealybugs)
Why it happens
High humidity and poor air circulation.
How to fix it
Treat with insecticidal soap or neem oil, and improve air circulation around the plant.
Care through the year
Spring
In spring, increase watering frequency as the plant begins its growing season. Fertilize every 4-6 weeks with a diluted cactus fertilizer.
Summer
During summer, ensure the plant receives full sun and monitor for signs of dehydration, watering every 2-4 weeks as needed.
Fall
In fall, gradually reduce watering as the plant prepares for dormancy. Stop fertilizing by late fall.
Winter
In winter, keep the plant in a warm location and water sparingly, about once every 4-6 weeks, to prevent root rot.
Toxicity & Safety
Astrophytum myriostigma is non-toxic to pets and children. However, ingestion of any plant material may cause mild gastrointestinal upset. It is always best to keep plants out of reach of curious pets and children.
Good to know
How often should I water my Astrophytum myriostigma?
Water your Astrophytum myriostigma every 2-4 weeks during the growing season, allowing the soil to dry out completely between waterings.
What type of soil is best for Astrophytum myriostigma?
A well-draining cactus mix with a pH of 6.0 to 7.0 is ideal for Astrophytum myriostigma to prevent root rot.
Why are my Astrophytum myriostigma leaves turning yellow?
Yellowing stems can indicate over-watering or poor drainage. Ensure the soil dries out completely before watering again.
What temperature does Astrophytum myriostigma prefer?
Astrophytum myriostigma thrives in temperatures between 70-100°F (21-38°C) during the day and can tolerate cooler nights.
How do I propagate Astrophytum myriostigma?
You can propagate Astrophytum myriostigma through seeds or offsets. For seeds, sow in a cactus mix and keep warm and moist until germination.
When should I repot my Astrophytum myriostigma?
Repot your Astrophytum myriostigma every 2-3 years or when roots grow out of the drainage holes, using fresh cactus mix.
Is Astrophytum myriostigma toxic to pets?
Astrophytum myriostigma is non-toxic to pets and children, but ingestion may cause mild gastrointestinal upset.
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