19. Oenothera rosea L’Héritier ex Aiton, Hort. Kew. 2: 3. 1789.
Gaura epilobia Seringe; Godetia heuckii Philippi; Hartmannia rosea (L’Héritier ex Aiton) G. Don; H. rosea var. parvifolia (J. M. Coulter) Small; H. virgata (Ruíz & Pavon) Spach; Oenothera psycrophila Ball; O. rosea var. parvifolia J. M. Coulter; O. rubra Cavanilles; O. virgata Ruíz & Pavon; Xylopleurum roseum (L’Héritier ex Aiton) Raimann
Herbs perennial, caulescent, strigillose and often also sparsely hirsute; from slender taproot. Stems 1–several, ascending to decumbent, 7–65 cm. Leaves 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. Inflorescences erect. Flowers 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. Capsules 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. Seeds narrowly obovoid, 0.5–0.9 × 0.3–0.5 mm. 2n = 14.
Flowering Mar–Sep. Disturbed habitats, along creeks, low, weedy places; 10–600 m; Ariz., Calif., Tex.; Mexico; West Indies; Central America; introduced in South America (Argentina), Europe, Asia, s Africa, Atlantic Islands (Azores, Canary Islands); tropical areas.
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.
