Astrophytum myriostigma cv. ‘ONZUKA’ fma. quadricostatum
This is a nursery produced cultivar (Japan). This form has four ribs instead of the typical five, although with age it’s possible a 5th rib could grow. The plant grows best in sun to part shade. Water in the summer but let it dry out during the winter. The flower is a yellow color. This plant is on its own roots.