Oenothera albicaulis

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Herbs winter-annual, densely strigillose, also sparsely villous; from a taproot. Stems ascending to decumbent, 1–several from base, sometimes unbranched, erect or ascending, 5–30 cm. Leaves in a basal rosette and cauline, 1.5–10 × 0.3–2.5 cm; blade oblanceolate to oblong, margins subentire or coarsely dentate or pinnatifid. Flowers 1–3 opening per day near sunset; buds nodding, weakly quadrangular, without free tips; floral-tube 15–30 mm, mouth glabrous; sepals 15–30 mm; petals white, fading pink, usually obcordate, sometimes obovate, (15–) 20–35 (–40) mm; filaments 11–17 mm, anthers 6–10 mm; style 25–50 mm, stigma exserted beyond anthers at anthesis. Capsules ascending to erect, usually straight, sometimes curved, cylindrical, weakly 4-angled, 20–40 × 3–4 mm, dehiscent 1/2 their length; sessile. Seeds in 2 rows per locule, ellipsoid to subglobose, 0.8–1.5 × 0.5–0.9 mm, surface regularly pitted, pits in longitudinal lines. 2n = 14.

Phenology: Flowering (Feb–)Mar–Jun(–Dec).
Habitat: Dry, usually sandy flats and slopes.
Elevation: 1000–2300 m.

Ariz., Colo., Idaho, Kans., Mont., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Utah, Wyo., Mexico (Chihuahua), Mexico (Sonora)

Discussion

Oenothera albicaulis is self-incompatible (W. L. Wagner et al. 2007; K. E. Theiss et al. 2010). Oenothera albicaulis has been reported from southern Nevada, but documentation is needed of its occurrence there.

Anogra pinnatifida Spach, Baumannia pinnatifida Spach, Oenothera pinnatifida Nuttall, O. purshiana Steudel, and O. purshii G. Don are illegitimate names that pertain here.

Selected References

None.

Lower Taxa