Herbs perennial, densely strigillose, sometimes also villous, or glabrous; from a taproot, lateral roots producing adventitious shoots, or rarely with fleshy underground horizontal rootstock (subsp. eurekensis). Stems ascending or decumbent, usually branched from near base, sometimes new rosettes forming at branch apex when buried in drifting sand, 10–60 cm. Leaves in a basal rosette and cauline, rosette sometimes weakly developed or absent, at least during flowering, 1–13 × 0.5–2 cm; petiole 0–2(–4.5) cm; blade oblong to oblanceolate or spatulate, sometimes rhombic-ovate, margins entire or weakly to conspicuously dentate or pinnatifid. Flowers 1–several opening per day near sunset; buds nodding, weakly quadrangular, with free tips 0–0.8 mm; floral tube 20–40 mm; sepals 15–30 mm, not spotted; petals white, fading pink to deep pink, broadly obcordate, 15–35(–40) mm; filaments 10–17 mm, anthers 5–10 mm; style 30–60 mm, stigma exserted beyond anthers at anthesis. Capsules spreading to ascending, woody in age, often curved upward, cylindrical, obtusely 4-angled, tapering slightly from base to apex, 20–80 × 2–3.5 mm; sessile. Seeds numerous, in 1 row per locule, olive-brown or yellowish brown to black, sometimes with minute purple dots, obovoid, 1–2.5 mm.

Discussion

Subspecies 3 (3 in the flora): w United States, nw Mexico.

Most populations of Oenothera californica are self-incompatible (W. L. Wagner et al. 2007; K. E. Theiss et al. 2010), but some populations of subsp. californica are self-compatible. All chromosome counts indicate that subspp. avita and eurekensis are diploid (2n = 14) and those of subsp. californica are tetraploid (2n = 28). Oenothera californica is polymorphic with subspp. avita and californica being very similar, and differing primarily in ecology, distribution, and relatively minor differences in leaf morphology and ploidy level, while the sand dune-restricted subsp. eurekensis is more distinctive in both morphology and habitat.

Selected References

None.

Lower Taxa

Oenothera avita subsp. avita, Oenothera avita subsp. californica, Oenothera avita subsp. eurekensis

Key

1	Plants with fleshy underground horizontal rootstocks; stems sometimes with new rosettes forming at stem apex when becoming buried in drifting sand; leaf blades rhombic-ovate to oblanceolate, margins entire or weakly dentate.	Oenothera californica subsp. eurekensis
1	Plants with a taproot and adventitious shoots from lateral roots; stems not with new rosettes forming at branch apex; leaf blades oblong to oblanceolate to spatulate, margins entire or weakly to conspicuously dentate or pinnatifid.	> 2
2	Leaf blade margins usually entire or weakly dentate, sometimes more conspicuously dentate to pinnatifid; capsules 30–55 mm.	Oenothera californica subsp. californica
2	Leaf blade margins conspicuously dentate to pinnatifid, rarely some or all of them entire or weakly dentate; capsules 20–80 mm.	Oenothera californica subsp. avita