Herbs perennial (short-lived or, sometimes, suffrutescent) or annual, glabrous or strigillose; from a stout taproot. Stems 1–many, weakly decumbent to ascending or erect, unbranched to moderately branched, (10–)25–80 cm. Leaves 1–9 × (0.1–)0.3–1 cm, sometimes fascicles of small leaves to 2 cm present in non-flowering axils; petiole 0–0.6 cm; blade linear to narrowly lanceolate or oblanceolate, often folded lengthwise, usually not much reduced distally, proximalmost leaves sometimes spatulate, base attenuate, margins subentire or serrulate or spinulose-serrate, apex acute. Flowers opening at sunrise; buds with free tips 0–4 mm; floral tube 5–20 mm; sepals 4–12 mm, midribs keeled; petals yellow, fading orangish to purplish, 6–25 mm; antisepalous filaments 2–8 mm, antipetalous filaments 1–4 mm, anthers 2–7 mm, pollen 90–100% fertile; style 9–30 mm, stigma sometimes blue-black, discoid to quadran­gular, exserted beyond anthers. Capsules 10–35 × 1–2 mm, hard, dehiscent 1/2 their length, often tardily dehiscent throughout their length. Seeds obo­void, 1–1.8 mm, sharply angled, apex truncate.

Discussion

Subspecies 2 (2 in the flora): c, sc United States, n Mexico.

Oenothera capillifolia is self-incompatible (H. F. Towner 1977).

Oenothera berlandieri (Spach) Steudel 1841, not D. Dietrich 1840, is superfluous and cannot be used in Oenothera when transferred from Calylophus, and pertains here.

Selected References

None.

Lower Taxa

Oenothera capillifolia subsp. berlandieri, Oenothera capillifolia subsp. capillifolia

Key

1	Stems 1–several, ascending to erect, 30–80 cm; leaves 2.5–9 cm.	Oenothera capillifolia subsp. capillifolia
1	Stems several–many, decumbent to ascending, (10–)25–40 cm; leaves 1–4 cm.	Oenothera capillifolia subsp. berlandieri