Oenothera hirtella Greene, Fl. Francisc., 215. 1891; Camissonia hirtella (Greene) P. H. Raven; O. hirta Link var. jonesii H. Léveillé; O. micrantha Hornemann ex Sprengel var. hirtella (Greene) Jepson; O. micrantha var. jonesii (H. Léveillé) Munz; O. micrantha var. reedii (Parish) Jepson; Sphaerostigma arenicola A. Nelson; S. bistortum (Nuttall ex Torrey & A. Gray) Walpers var. reedii Parish; S. hirtellum (Greene) Small; S. hirtellum var. montanum Davidson; S. micranthum (Hornemann ex Sprengel) Walpers var. jonesii (H. Léveillé) A. Nelson

Herbs annual, densely villous throughout, also glandular puberulent distally. Stems erect, with 1 or more ascending branches from near base, to 60 cm. Leaves 1–11 × 0.3–2.1 cm; petiole 0–5 cm, distal ones 0–0.5 cm; blade lanceolate to ovate, sometimes elliptic-ovate or ovate distally, base cordate to truncate, sometimes cuneate or attenuate, margins dentate, apex acute. Flowers opening near sunrise; floral tube 1–3 mm; sepals 2.5–6 mm; petals yellow, sometimes red-dotted near base, 2–9 mm, sometimes with a tooth arising from emarginate apex; episepalous filaments 1.2–6 mm, epipetalous filaments 0.5–3 mm, anthers 0.4–1 mm, less than 5% of pollen grains 4- or 5-pored; style 2–8 mm, stigma surrounded by anthers at anthesis. Capsules 1–2-coiled spiral, subterete in living material, 4-angled when dry, 13–20(–25) × 0.7–0.9 mm. Seeds 1–1.2 mm. 2n = 14.

Flowering (Jan–)Mar–Jul(–Nov). Brushy hills and slopes, on burns; 0–2300 m; Calif.; Mexico (Baja California).

Camissoniopsis hirtella occurs from Amador and Trinity counties southward in the Coast Ranges and Sierra Nevada of California to the Sierra de Juárez and Sierra San Pedro Mártir, Baja California, usually away from the immediate coast and barely reaching the margins of the desert. P. H. Raven (1969) determined C. hirtella to be self-compatible and primarily autogamous. The species occasionally hybridizes with C. ignota (Raven).