Seeds from Acanthocalycium violaceum Acanthocalycium spiniflorum cactus. This solitary to slowly clumping castus grows to 24 inches tall and 6 to 7 inches wide. Direct sow seeds after last frost,although fairly slow to germinate. It is a summer-growing species that offers no cultivation problems. It needs good drainage and very porous substrate. Water regularly in summer, but do not overwater. Wait for the well draining soil mixture to be rather dry before watering again. Keep rather dry in winter. Feed with a high potassium fertilizer in summer. Hardy to 12 degrees.