Oenothera rosea
Oenothera pilosella
pink evening primrose, rose evening-primrose
meadow evening-primrose
1–several, ascending to decumbent, 7–65 cm.
spreading or ascending, unbranched or few-branched distally, 20–80 cm.
in a basal rosette and cauline, basal 1–6 × 0.3–2 cm, blade narrowly elliptic to elliptic or ovate, margins subentire, weakly serrulate, or sinuate-pinnatifid;
cauline 1–6 × 0.3–2 cm, blade narrowly elliptic to narrowly ovate, margins subentire or weakly serrulate, proximal ones sinuate-pinnatifid.
in a basal rosette and cauline, basal 4–8 × 2–5 cm, petiole (0.5–)1–3(–4) cm, blade oblanceolate to ovate, margins entire;
cauline 3–10(–13) × 1–2(–4) cm, petiole 0–0.5(–2) cm, blade lanceolate to ovate, abruptly narrowed to base, margins subentire or coarsely dentate.
erect.
erect, flowers in axils of distalmost few nodes.
1–3 opening per day near sunrise;
buds with free tips 0.1–1 mm;
floral tube 4–8 mm;
sepals 6–12 mm;
petals rose purple, fading darker, 4–12 mm;
filaments 4–6 mm, anthers 2–3.5 mm, pollen 35–65% fertile;
style 7–13.5 mm, stigma surrounded by anthers at anthesis.
opening near sunrise;
buds with free tips 1–3 mm, spreading;
floral tube 10–25 mm;
sepals 10–20 mm;
petals bright yellow, fading pale pink or pale yellow, 15–30 mm;
filaments 7–15 mm, anthers 4–8 mm, pollen 85–100% fertile;
style 10–20 mm, stigma exserted beyond anthers at anthesis.
narrowly obovoid, 4–12 × 2–4 mm, apex attenuate to a sterile beak, proximal stipe 5–20 mm, gradually tapering to base, valve midrib prominent in distal part;
sessile.
usually oblong-clavate to oblong-ellipsoid or ellipsoid, 4-angled or weakly 4-winged, (5–)10–15(–28) × 2–4(–5) mm, stipe (1–)3–5(–9) mm;
sessile.
narrowly obovoid, 0.5–0.9 × 0.3–0.5 mm.
1 × 0.5 mm.
= 14.
= 56.
Oenothera rosea
Oenothera pilosella
Oenothera rosea is a PTH species, forming a ring of 14 chromosomes in meiosis, and is self-compatible and autogamous. In the flora area, it is known from Cochise, Pima, and Santa Cruz counties in Arizona, Alameda, Los Angeles, Riverside, San Bernardino, San Diego, San Francisco, and Santa Barbara counties in California (primarily in urban areas), and from southern Texas. It is clearly of North American origin, since all of its close relatives are confined to North America, and has spread south along the Andes. It occurs at 500–3700 m in South America but generally at lower elevations in most areas.
The name Hartmannia affinis Spach is illegitimate, being based on Oenothera virgata; H. gauroides Spach is also illegitimate, being based on O. rosea; O. purpurea Lamarck is a later homonym; these three names pertain here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Oenothera pilosella is widespread in cultivation in gardens and frequently escapes and becomes naturalized; the northern and eastern natural limits of O. pilosella are not clear. According to G. B. Straley (1977) the natural limits are from Wayne County, West Virginia, along the Ohio River and Erie County, New York, for the eastern limits, and Tuscola County, Michigan, and Manitowoc County, Wisconsin, for the northern limits. K. N. Krakos (2014), based on new field studies and phylogenetic data, found that O. pilosella does not form a monophyletic group with plants previously treated by Straley as O. pilosella subsp. sessilis in molecular analyses, and thus is here reinstated as the distinct species O. sessilis. Straley determined that O. pilosella is self-incompatible and an octoploid, one of the few in the genus.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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