Astrophytum asterias (Sand Dollar Cactus, Sea Urchin Cactus)
The Astrophytum asterias AKA Sand Dollar Cactus is a popular spineless
cactus. In the wild it is almost extinct, mostly due to habitat
destruction. It decreases in size when lacking water.
Astrophytum asterias--San Dollar Cactus prefer alkaline, porous soil.
Water slightly more in summer during its growing season. You can use half
strength liquid fertilizer after the flower buds have formed.