Plants to 2.5 dm; roots elongate, fleshily woody. Stems ± erect, simple or sometimes branching. Leaves sessile; blade terete, to 6 cm. Inflorescences cymose, much overtopping leaves; peduncle scapelike, to 15 cm. Flowers: sepals deciduous, ovate, 4 mm; petals pink to magenta, ovate to obovate, sometimes mucronulate, 6.5-8 mm; stamens 12-28; stigmas 3, spreading widely, linear, 1/2-1/3 as long as styles. Capsules subglobose, 4 mm. Seeds without arcuate ridges, 1.2 mm, corrugate-rugulose overall. 2n = 24. Flowering May-Aug. Sand or sandy soils, dunes, mounds, flats, banks, ridges, edges of igneous or metamorphic rock outcrops, along or near watercourses; 0-500 m; Ill., Ind., Iowa, Kans., La., Minn., Nebr., Tex., Wis. Within the overall area of its distribution, Phemeranthus rugospermus is nowhere abundant, its occurrence being everywhere spotty and localized. According to T. S. Cochrane (1993), the disjunctions probably reflect a history of long-distance dispersal from a center in the partially unglaciated Kansas and Nebraska sandhills, the present-day gaps resulting from a paucity of suitable habitats between that area and the others where it is now found. Even so, its discovery in Missouri, Arkansas, and/or Oklahoma would not be surprising.
