Gaurella canescens (Torrey & Frémont) A. Nelson; Megapterium canescens (Torrey & Frémont) Britton; Oenothera guttulata Geyer ex Hooker

Herbs low, forming clumps 10–50 cm diam., densely strigillose throughout; from a taproot, lateral roots producing adventitious shoots. Stems many-branched from base, leafy, (10–)15–25(–38) cm. Leaves cauline, (0.3–)0.6–1.5(–2.5) × (0.05–)0.15–0.4(–0.6) cm, fascicles of small leaves 0.2–0.6 cm often present in non-flowering axils; petiole 0–0.1 cm; blade lanceolate to linear, base cuneate, apex acute. Flowers several opening per day near sunset; buds usually without free tips, rarely free tips 0.2–0.3 mm; sepals (7–)8–12 mm; petals pink, rarely white, streaked or flecked with red, fading bright purple, (8–)10–17 mm; filaments 6–8 mm, anthers often with red longitudinal stripe, 3–6 mm; style (16–)22–27 mm, stigma exserted beyond anthers at anthesis. Capsules woody, ovoid, narrowly winged, wings 0.8–1.5 mm wide, (7–)9–12(–14) × 2–4 mm (excluding wings), abruptly constricted to a conspic­uous, sterile beak, (2–)3–4.5 mm, indehiscent; sessile. Seeds asymmetrically cuneiform or oblanceoloid, 1.2–1.5 × 0.4–0.5 mm. 2n = 14.

Flowering May–Aug. Prairie depressions, playas, margins of ditches, temporary wet areas; (400–)700–1800 m; Colo., Kans., Nebr., N.Mex., Okla., Tex., Wyo.

Oenothera canescens is restricted to prairie depres­sions, playas, ditch margins, and other places of temporary water in the High Plains of the western United States from Goshen County, Wyoming, south­east to Hayes County, Nebraska, south through eastern Colorado, the eastern tier of counties in New Mexico, western Kansas, and to Garza and Dawson counties in the Texas Panhandle; also disjunct populations from Chautauqua, Sedgwick, and Stafford counties, Kansas.

The illegitimate names Gaurella guttulata (Geyer ex Hooker) Small, G. canescens (Torrey & Frémont) Cockerell, and Gauropsis guttulata (Geyer ex Hooker) Cockerell pertain here.