Origin and Natural Habitat
Ariocarpus retusus is indigenous to Mexico.
These plants were grown from seed in South Africa, and were not imports or degrafts.
Plant Characteristics
Ariocarpus retusus is a gray-green, star-shaped cactus with an attractive symmetrical stem. This species produces interesting ‘wool’ near the growth points once it gets older. It is generally spineless. Makes white or light-pink flowers in spring and summer.
Care Guide
Light
Ariocarpus can tolerate full morning sun if carefully adjusted to it, but a plant grown in some shade or a newly replanted specimen should not be placed in full sun immediately. It is best to grow them under 40% shade cloth.
Soil
Ariocarpus retusus 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 autumn and winter. Ariocarpus are extremely prone to rot if watered in winter.
Pot size
Ariocarpus retusus are medium sized cacti when mature. This species tends to remain solitary and does not produce offshoots at all, unless the growth point is damaged. 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 25 – 35°C. It can tolerate 5 – 35°C. It is sensitive to frost.
Humidity
Ariocarpus retusus are sensitive to humidity, particularly during winter. This species tends to rot in high humidity. 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
Ariocarpus retusus 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
Ariocarpus retusus are best propagated from seed.
Seed germination: Seeds should be sown in early spring. Plant them in a well-drained 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 completely. Plant out after 1 year.