Oenothera hirta Link var. exfoliata (A. Nelson) Munz; O. micrantha Hornemann ex Sprengel var. exfoliata (A. Nelson) Munz; Sphaerostigma micranthum (Hornemann ex Sprengel) Walpers var. exfoliatum A. Nelson

Flowers: floral tube 1–3 mm; sepals (1.5–)2.5–5.5 mm; petals rarely with red dots basally, (2–)3.5–6(–8) mm; episepalous filaments (0.5–)1.5–4 mm, epipetalous filaments (0.2–)0.5–2.2 mm, anthers (0.4–)0.8–1.2 mm; style (2.1–)3–6.5 mm. 2n = 14.

Flowering (Jan–)Mar–Aug(–Nov). Desert slopes and flats, along washes, creosote bush scrub, Joshua tree woodlands; 30–1900 m; Ariz., Calif., Nev.; Mexico (Baja California).

Subspecies pallida occurs from the head of the San Joaquin Valley in Ventura and Kern counties, California, across the Colorado and Mojave deserts, north to the vicinity of Independence, Inyo County, California, and Esmeralda County, Nevada (the only member of the genus in Nevada), east to Mohave and Yavapai counties, Arizona, and also in the vicinity of Tucson, Pima County; also south along the eastern side of Baja California to the Sierra de San Borjas, Mexico.