Origin and Natural Habitat
Astrophytum asterias is native to certain areas of Texas and Mexico.
These plants were grown from seed in South Africa, and were not imports or degrafts.
Plant Characteristics
Astrophytum asterias is a dark-green, globular cactus with attractive white spots on the stem. Some specimens produce white ‘woolly’ spots from the areoles.
Care Guide
Light
Unlike most cacti, Astrophytum asterias are somewhat sensitive to full sun. It is best to grow them under 40%-60% shade cloth.
Soil
Astrophytum asterias is quite fussy and should only be planted in a gritty, inorganic soil medium that drains well, such as Ibaraki Akadama or Hyuga pumice.
Water
You should thoroughly soak the soil when watering. Only water this species in the spring and summer growing season, and keep dry in winter. Astrophytum are extremely prone to rot if watered in winter.
Pot size
Astrophytum asterias are medium sized cacti when mature. This species tends to remain solitary and does not produce offshoots at all. Small plants can be grown in 10cm pots until they start to grow near the edges of the pot, at which point they can be moved to larger pots. They should only be planted in a pot that is 3-5cm wider than their stem diameter.
Temperature
This species’ ideal temperature ranges between 20 – 30°C. It can tolerate 5 – 35°C. It is very sensitive to frost.
Humidity
Astrophytum are sensitive to humidity, particularly during winter. Make sure that your growing space has plenty of airflow.
Fertilizing
Use a half-strength diluted general liquid fertilizer only during the growing season. Do not fertilize during autumn or winter. Alternatively, a small amount of slow-release fertilizer will be sufficient.
Growing Season
Astrophytum asterias grow actively in spring and summer, and are fully dormant in autumn and winter.
In South Africa, their growing season is from October until late February.
Propagation
Astrophytum asterias are best propagated from seed.
Seed germination: Seeds should be sown in early spring. Plant them in a well-draining coco peat based mix in an airtight container. Once most of the seeds have germinated, remove the lid of the container to allow airflow. Gently mist the seedlings every few days so that the soil does not dry out.