Plants to 4 dm; roots fleshily woody. Stems ascending or erect, simple or branching. Leaves sessile; blade subterete, to 7 cm. Inflorescences cymose, much overtopping leaves; peduncle scapelike, to 25 cm. Flowers: sepals persistent, ovate to suborbiculate, 4-6 mm; petals pink- to red-purple, obovate, 10-15 mm; stamens 25-45; stigma 1, subcapitate, 3-lobed. Capsules broadly ovoid, 6-7 mm. Seeds without arcuate ridges, 1 mm. 2n = 24, 48. Flowering May-Oct. Rocky or sandy soil, on or near outcrops; 100-1200 m; Ark., Colo., Ill., Kans., La., Mo., Nebr., N.Mex., Okla., Tex. Some populations of Phemeranthus calycinus are diploid while others are tetraploid, the latter probably the result of autopolyploidy (W. H. Murdy and M. E. B. Carter 2001).
Infl 1-3 dm; sep prolonged at base like the bracts; pet 10-16 mm, deep rose-pink to rose-red; stamens 20-45; stigma capitate; fr 6-8 mm. Barrens and rocky ledges; s. Ill. and s. Mo. to Neb., Kans., and Tex. May, June. Fls open only in early to mid- afternoon.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.