Sclerocactus parviflorus

Sclerocactus is a genus that is considered to be notoriously difficult in culture, and plants are usually grown on graft. Proper stock allows plants look more or less naturally and often supports earlier and more proliferus flowering. My preferred stock for them is Opuntia humifusa.
If grown on own roots the natural cycle must be considered, with dry summers and wet winters. Larger plants are actually pretty robust, and in California climate do better if in winter kept outside of the greenhouse.