Astrophytum myriostigma
Light: Bright light with morning sun and afternoon shade in Phoenix; acclimate gradually to direct sun and protect from intense summer afternoon exposure.
Water: Low water; water thoroughly only after the soil dries completely during warm-season growth. Keep nearly dry in winter, especially during cold weather.
Soil: Very fast-draining, predominantly mineral cactus mix with pumice, gravel, or coarse grit; avoid moisture-retentive soil.
Mature size: Typically 12–24 inches tall and 6–10 inches wide over many years; old specimens may grow taller.
Bloom: Yellow flowers appear intermittently from spring through summer on mature plants, often beginning after several years.
Evergreen / deciduous: Evergreen succulent; persistent green stems with no visible foliage.
Growth rate: Slow.