A spineless, perfectly flat disc of a cactus native to semi-arid shrubland and gypsum outcrops across Tamaulipas to the southern tip of Texas. Known in Japanese cultivation as kabuto (兜), it is a sister species to A. myriostigma (鸞鳳玉) within the genus, sharing the spineless habit and scattered white woolly flecks common to Astrophytum. The body is typically eight-ribbed (ranging five to ten), marked with white trichome dots, and the crown opens a yellow flower with a reddish center. Listed on CITES Appendix II (the entire genus) and assessed as Endangered by the IUCN — habitat loss in Tamaulipas and illegal collection have severely reduced wild populations, and the species is protected under Mexican law. Most plants in circulation are nursery-raised from seed.
Native climate
Rainfall is spread fairly evenly across the year. Overall mild, with a wide temperature range.
* Accurate distribution data is scarce for this species, so these values are taken from the climate near the approximate center of its native range instead.
Sources: climate & elevation WorldClim 2.1 (1970–2000) · occurrences GBIF · native range POWO · current weather Open-Meteo
Care
Light & Placement
In habitat it grows in semi-arid lowland shrubland at 60–200 m in southern Texas and Tamaulipas under strong sun. Give it a bright, all-day position, but note that the flat disc profile makes the top surface particularly prone to epidermal scorch in harsh midsummer light. During the growing season, a light 20–30% shade cloth in the most intense weeks prevents surface burns without causing etiolation. Keep the pot in good airflow; a circulator helps. For winter dormancy, move to a bright indoor window above 5°C and water very sparingly.
Watering
Water thoroughly only after the substrate has fully dried, then let it dry out again. The flat, compact body holds less water than columnar species, making it particularly vulnerable to overwatering. In winter, a light misting once or twice a month is plenty.
Substrate
Drainage above all. The gypsum-outcrop origin means it tolerates a slightly alkaline lean. Small-grain Akadama : Kanuma : pumice = 4:3:3 with a small dose of dolomitic lime works well. A taller pot helps the wet-dry cycle and reduces rot risk.
Fertilizer & Supplements
A small amount of slow-release during active growth, plus a monthly dilute liquid feed (around twice the label dilution). Keeping feeding to a minimum preserves the compact, flat form that gives this species its character.
Temperature & Overwintering
Optimal 22–35°C. Overwinter dry on a bright window with a 5°C floor; cold combined with damp soil is the primary risk.
Starting from Seed
Where to source seeds
Pre-sowing treatment
Soak seeds for about half a day in a mix of a registered seed-treatment fungicide (Benlate or Daconil) and a plant tonic, each diluted per label. Cactus seed viability depends heavily on storage, so sowing soon after receipt is the safer course.
Substrate
Use a separate seedling mix that's fine-grained and near-sterile: fine Akadama, fine Kanuma, and vermiculite in equal 1:1:1 parts. Sterilize the mix with boiling water or a quick microwave pass before sowing.
Sowing method
Seeds are small to mid-sized; sow with no covering or only the thinnest dusting of substrate. Space seeds at least 1 cm apart and arrange them so they don't clump together on the surface.
Light & temperature
Keep the tray in bright shade at a steady 25–30°C. Expect germination in 3–14 days. With fresh seed, germination is on the easier side and tends to come up fairly quickly.
Watering
Bottom-water with the level 1–2 cm up the pot. For the first 2–3 weeks, prioritize not letting things dry out, then drop the water level in steady stages once seedlings emerge.
Fertilizer
No feeding right after germination. Once the flat disc shape starts to become recognizable, give a heavily diluted liquid fertilizer once or twice a month — go lighter than the bottle suggests, since young seedlings are easily pushed into etiolation.
From Germination to Repotting
Germination through true leaves (first month)
Keep bottom watering; manage in bright shade.
Weaning off bottom watering (months 1–2)
Lower the water level; switch to saucer watering.
First repotting (year 1–2)
Repot into a regular, primarily inorganic mix.
Common Pitfalls
Mold & damping-off
- Cause: contaminated substrate, excessive moisture, poor ventilation
- Prevention: sterilize the substrate, change the bottom water frequently, use an air circulator for ventilation
Etiolation & rib elongation
- Cause: insufficient light, overfeeding
- Prevention: bring the LED closer right after germination, or move the seedlings to bright shade outdoors
Seeds fail to germinate
- Cause: old seeds, insufficient temperature
- Prevention: choose a trusted source, stabilize temperature with a heat mat
Epidermal scorch
- Cause: abrupt strong light, unshaded midsummer sun (the flat top surface is particularly exposed)
- Prevention: change conditions gradually; add 20–30% shade in high summer
Notes
Spineless, but the flat body bruises easily on contact.
