Sanddollar
Astrophytum asterias · Sand Dollar Cactus · Sea Urchin Cactus · Star Peyote · Seaurchin Starcactus · Star CactusUSDA | Grow Zone
10-11Outdoors all year in zones 10 to 11. Anywhere colder, keep it as a houseplant. Protect it below 40°F.
- Light
- Full sun, 6-8 hours
- Water
- When soil is dry
- Humidity
- 30-40% preferred
- Temperature
- 70-100°F (21-38°C)
- Difficulty
- Beginner
- Growth
- Slow
- Mature size
- 6-12 inches diameter
- Pets
- Non-toxic to pets
Astrophytum asterias, commonly known as the Sand Dollar Cactus, is a unique and striking succulent native to Mexico. Its distinctive shape and minimal care requirements make it a popular choice among plant enthusiasts.
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Ideal temperature
50-100°F is where it grows fastest. Below 40°F cold damage starts.
Spacing and harvest
- Mature size
- 6-12 inches diameter
- Plant apart
- 6-12 in
- Frost
- Half hardy: light frost only
Everything it needs
9 essentials at a glance
Watering
Astrophytum asterias prefers infrequent watering, allowing the soil to dry out completely between waterings.
During the growing season (spring and summer), water every 2-3 weeks, reducing to once a month in fall and winter. Signs of over-watering include yellowing and mushy stems, while under-watering may cause shriveling and a lack of growth.
Light
This cactus thrives in full sun, ideally receiving at least 6-8 hours of direct sunlight daily.
A south-facing window or a bright greenhouse is ideal. While it can tolerate some partial shade, too little light can lead to etiolation, where the plant stretches and becomes leggy.
Soil
Astrophytum asterias prefers a well-draining soil mix, ideally a cactus or succulent potting mix with added perlite or sand to enhance drainage.
The ideal pH range is between 6.0 and 7.0. Ensure the pot has drainage holes to prevent water retention.
Humidity
This cactus prefers low humidity levels, ideally around 30-40%.
To increase humidity, you can place a humidity tray filled with water and pebbles beneath the pot, but avoid direct contact with water. Signs of humidity stress include browning or shriveling of the plant.
Temperature
Astrophytum asterias thrives in temperatures between 70-100°F (21-38°C) during the day and can tolerate down to 50°F (10°C) at night.
It is hardy in USDA zones 10-11, but should be protected from frost and extreme cold.
Fertilizing
Use a balanced cactus fertilizer with an NPK ratio of 10-10-10 or a low-nitrogen fertilizer diluted to half strength during the growing season, applying every 4-6 weeks.
Signs of nutrient deficiency include slow growth and pale coloration.
Pruning
Pruning is generally not necessary for Astrophytum asterias.
However, if you notice any dead or damaged parts, use sterilized scissors to remove them. Regularly check for pests and remove any affected areas to maintain plant health.
Repotting
Repot every 2-3 years or when the plant outgrows its pot, typically in spring.
Choose a pot that is 1-2 inches larger in diameter. Signs it needs repotting include roots growing out of the drainage holes or stunted growth. Carefully remove the plant from its pot, shake off excess soil, and place it in the new pot with fresh soil.
Propagation
Propagation is typically done through seeds, which should be sown in a well-draining mix.
The best time to sow seeds is in spring. Lightly cover the seeds with soil, mist them, and keep them warm and humid until germination occurs, usually within 2-4 weeks.
When it's unhappy
Yellowing stems
Why it happens
Over-watering or poor drainage.
How to fix it
Reduce watering frequency and ensure the pot has adequate drainage.
Shriveling
Why it happens
Under-watering or insufficient light.
How to fix it
Increase watering frequency and ensure the plant receives enough sunlight.
Browning tips
Why it happens
Low humidity or excessive direct sunlight.
How to fix it
Increase humidity levels or provide some afternoon shade.
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.
Etiolation
Why it happens
Insufficient light.
How to fix it
Move the plant to a brighter location to encourage compact growth.
Care through the year
Spring
In spring, resume regular watering and fertilizing as the plant enters its active growth phase. Monitor for pests and repot if necessary.
Summer
During summer, ensure the cactus receives plenty of sunlight and water every 2-3 weeks, allowing the soil to dry out completely between waterings.
Fall
In fall, gradually reduce watering frequency as the plant prepares for dormancy. Stop fertilizing by late fall.
Winter
In winter, water sparingly, only when the soil is completely dry. Keep the plant in a warm location, avoiding cold drafts.
Toxicity & Safety
Astrophytum asterias is considered non-toxic to pets and children. However, ingestion of any plant material can cause mild gastrointestinal upset. Always supervise pets around plants.
Good to know
How often should I water my Astrophytum asterias?
Water your Sand Dollar Cactus every 2-3 weeks during the growing season, allowing the soil to dry out completely between waterings.
What light conditions are best for Astrophytum asterias?
This cactus thrives in full sun, requiring at least 6-8 hours of direct sunlight daily for optimal growth.
What type of soil is ideal for Astrophytum asterias?
Use a well-draining cactus mix, ideally with added perlite or sand, to ensure proper drainage and prevent root rot.
How can I propagate Astrophytum asterias?
Propagate through seeds sown in spring in a well-draining mix. Keep them warm and humid until germination occurs.
What temperature range is best for Astrophytum asterias?
This cactus prefers temperatures between 70-100°F (21-38°C) and can tolerate down to 50°F (10°C) at night.
Is Astrophytum asterias toxic to pets?
Astrophytum asterias is non-toxic to pets and children, but ingestion can cause mild gastrointestinal upset.
When should I repot my Astrophytum asterias?
Repot every 2-3 years or when the plant outgrows its pot, typically in spring, using fresh soil.
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