Herbs usually winter-annual, sometimes perennial, glabrous, glandular puberulent, strigil­lose, and/or villous, sometimes more villous distally, hairs sometimes very curly, espe­cially on flower parts; from a taproot or relatively long, fleshy roots. Stems: central stem usually erect, usually thickened at base and spongy, branched or unbranched, branches few–several, slender, decumbent to ascending, from base, usually encircling central stem in older plants, 10–40(–100) cm. Leaves in a basal rosette and cauline, rosette usually well developed (except subsp. howellii), basal 5–25 × 1–5 cm, cauline 4–12(–18) × 0.5–4 cm; petiole 1.5–8 cm; blade rhombic-obovate, lanceolate, or oblance­olate, margins subentire, dentate, or pinnatifid. Flowers 1–several opening per day near sunset; buds nodding, weakly or strongly quadrangular or fluted in distal 1/2, with free tips 0–9 mm; floral tube 20–40 mm; sepals (13–)15–35 mm, not spotted; petals white, fading pink to deep pink, broadly obo­vate or obcordate, 15–44 mm; filaments 8–15 mm, anthers 5–14 mm; style 35–60 mm, stigma exserted beyond anthers at anthesis. Capsules spreading, straight to curved, becoming somewhat woody in age, cylindrical to slightly 4-angled, widest toward base, tapering from base to apex, (15–)30–80 × 1.5–5 mm; sessile. Seeds numerous, in 1 row per locule, buff with dark spots or black, narrowly obovoid, 1.5–2.8 mm.

Discussion

Subspecies 5 (5 in the flora): w United States, nw Mexico.

Oenothera deltoides is self-incompatible or self-compatible (W. M. Klein 1964; W. L. Wagner et al. 2007; K. E. Theiss et al. 2010).

Selected References

None.

Lower Taxa

Oenothera deltoides subsp. ambigua, Oenothera deltoides subsp. cognata, Oenothera deltoides subsp. deltoides, Oenothera deltoides subsp. howellii, Oenothera deltoides subsp. piperi

Key

1	Herbs perennial, from long, fleshy roots; stems not thickened at base, branches erect or ascending, not encircling stems in older plants.	Oenothera deltoides subsp. howellii
1	Herbs annual or short-lived perennial from a taproot; stems usually thickened at base, branches ascending or decumbent, often encircling stems in older plants.	> 2
2	Flower buds fluted or strongly quadrangular in distal 1/2, without free tips, villous with curly hairs, sometimes glabrous; leaf blade margins sinuate-dentate to pinnatifid; petals 15–25(–30) mm; capsules 15–25(–30) mm.	Oenothera deltoides subsp. piperi
2	Flower buds weakly or strongly quadrangular in distal 1/2, with free tips 0–3 mm, strigillose, sparsely to moderately villous, or glabrous; leaf blade margins sinuate-dentate or subentire, rarely pinnatifid; petals 15–44 mm; capsules 40–80 mm.	> 3
3	Flower buds with free tips 1–3 mm, quadrangular in distal 1/2; plants strigillose, especially distally.	Oenothera deltoides subsp. ambigua
3	Flower buds with free tips 0–1.5 mm, weakly quadrangular in distal 1/2; plants glabrous, villous, or strigillose.	> 4
4	Herbs annual, strigillose, sometimes also villous; capsules 2–3.5 mm diam.; flower buds with free tips 0–1.5 mm.	Oenothera deltoides subsp. deltoides
4	Herbs short-lived perennial or some­times annual, glabrous or sparsely villous, rarely also strigillose; capsules 3–5 mm diam.; flower buds without free tips.	Oenothera deltoides subsp. cognata