Oenothera rosea
Oenothera sect. Hartmannia
pink evening primrose, rose evening-primrose
1–several, ascending to decumbent, 7–65 cm.
decumbent to ascending or erect, usually branched, sometimes unbranched.
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, cauline 1–6(–10) cm;
blade margins subentire, weakly serrate to weakly sinuate-toothed, sometimes sinuate-pinnatifid.
erect.
solitary flowers in axils of distal leaves.
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 or sunset;
buds erect, terete, without free tips or free tips minute (except to 4 mm in O. speciosa);
floral tube 4–26 mm;
sepals splitting along one suture, remaining coherent and reflexed as a unit at anthesis or, rarely, separating in pairs;
petals usually pink or rose purple, fading darker, rarely white, fading pink, obovate to obcordate;
stigma deeply divided into 4 linear lobes.
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.
hard and leathery, straight, clavate or narrowly obovoid to rhombic-ellipsoid, angled or narrowly winged (to 0.5 mm, apex attenuate to a sterile beak, proximal part tapering to a sterile, pedicel-like base (stipe), valve midrib raised (prominent in O. speciosa), dehiscent at apex or nearly throughout fertile part;
sessile.
narrowly obovoid, 0.5–0.9 × 0.3–0.5 mm.
numerous, clustered in each locule, narrowly obovoid, surface glossy, appearing granular, but minutely papillose under magnification.
= 14.
= 14, 28, 42.
Oenothera rosea
Oenothera sect. Hartmannia
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.)
Species 5 (4 in the flora).
Section Hartmannia consists of five species, mostly diploid (2n = 14), but Oenothera speciosa is diploid and also has polyploid populations (2n = 28, 42). All of the species are morphologically very similar, characterized by purple to pink (or white in O. speciosa) petals, leaves often lobed toward the base or distally, capsules often straight, with the fertile portion of the capsule relatively short, angled or narrowly winged (less than 5 mm), apex attenuate, tapering to an acute beak. All species form a definite rosette, which persists at least until the onset of flowering, and ascending to decumbent stems. Most of the species occur in an area from Arizona and Texas south into Mexico, but O. speciosa extends to the Central Plains in the United States, and O. rosea also ranges farther to Central America, the Caribbean (Bermuda, Hispaniola, Jamaica), and northern South America to central Chile. Only Oenothera deserticola (Loesener) Munz occurs outside the area and is restricted to high elevations in the Trans-Volcanic Belt of Mexico. Oenothera rosea is widely naturalized worldwide in tropical and subtropical areas. Four species form bivalents in meiosis, and are self-compatible, except for O. speciosa, which is self-incompatible. Oenothera rosea is a PTH species and forms a ring of 14 chromosomes in meiosis, and is self-compatible and autogamous. Oenothera speciosa has mostly diploid (2n = 14) populations with vespertine or diurnal white flowers in the northern part of its range; many of those from central Texas southward are morning-opening, pink-flowered, and mostly tetraploid (2n = 28) or hexaploid (2n = 42). Pollinators are primarily bees, noctuids, and very few hawkmoths (in O. speciosa), and sometimes secondarily skippers and other butterflies (summarized by W. L. Wagner et al. 2007).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Inflorescences sharply nodding; capsule stipes cylindrical. | O. speciosa |
1. Inflorescences erect; capsule stipes gradually tapering to base. | → 2 |
2. Floral tubes 4–8 mm; sepals 6–12 mm; petals 4–12 mm; pollen 35–65% fertile. | O. rosea |
2. Floral tubes 9–26 mm; sepals 7.5–23 mm; petals 8–25(–30) mm; pollen 85–100% fertile. | → 3 |
3. Floral tubes 9–14 mm; sepals 7.5–12 mm; petals 8–15 mm; styles 12–19 mm; plants strigillose, often densely so. | O. platanorum |
3. Floral tubes 15–26 mm; sepals 15–23 mm; petals 12–25(–30) mm; styles 26–36 mm; plants strigillose, also sparsely hirsute. | O. texensis |
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