Ariocarpus trigonus. Sunset: 11,13; USDA: 9b-11. Hardy to 27° F. Full sun to light shade, needs protection in hottest desert gardens. Solitary spineless, slowly growing up to 12" in diameter, 10" tall. Little water summer, no water in winter. Needs limestone in soil, soil must have good drainage. 1- 2" white to yellowish white flowers with a satin sheen. Origin: Mexico at 2000 to 4000 feet.