Oenothera pilosella |
Oenothera rhombipetala |
|
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meadow evening-primrose |
fourpoint evening primrose |
|
Habit | Herbs perennial, usually densely to sparsely hirsute, rarely glabrous; from a thickened base, rhizomatous. | Herbs biennial, densely to sparsely strigillose, sometimes also sparsely glandular puberulent distally. |
Stems | spreading or ascending, unbranched or few-branched distally, 20–80 cm. |
sometimes with lateral branches arising obliquely from rosette, 30–100(–150) cm. |
Leaves | 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. |
in a basal rosette and cauline, basal 6–20 × 0.6–2 cm, cauline 3–15 × 0.8–2.5 cm; blade narrowly oblanceolate, gradually narrowly elliptic to narrowly lanceolate, oblanceolate, or ovate distally, margins lobed to remotely dentate or subentire; bracts slightly longer than capsule they subtend. |
Inflorescences | erect, flowers in axils of distalmost few nodes. |
dense, usually without lateral branches, mature buds usually not overtopping spike apex. |
Flowers | 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. |
2–several per spike opening per day near sunset; buds erect, with free tips erect, 0.5–3 mm; floral tube slightly curved upward to ± straight, 30–45 mm; sepals 15–30 mm; petals yellow, broadly elliptic to rhombic-elliptic, 15–35 mm; filaments 13–25 mm, anthers 3–8 mm, pollen 85–100% fertile; style 25–50 mm, stigma exserted beyond anthers at anthesis. |
Capsules | 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 lanceoloid, 13–25 × 2.5–3 mm. |
Seeds | 1 × 0.5 mm. |
brown, sometimes flecked with dark red spots, ellipsoid, 1–1.7 × 0.4–0.7 mm. |
2n | = 56. |
= 14. |
Oenothera pilosella |
Oenothera rhombipetala |
|
Phenology | Flowering May–Jul(–Aug). | Flowering May–Oct. |
Habitat | Open fields, edge of woods, marshes and bottomland prairies, open disturbed sites, ditches, old fields, railroads, roadsides. | Fields, prairies, sandy soil. |
Elevation | 100–600 m. (300–2000 ft.) | 60–600(–1300) m. (200–2000(–4300) ft.) |
Distribution |
AL; AR; CT; IA; IL; IN; KY; LA; MA; ME; MI; MO; MS; NH; NY; OH; OK; PA; RI; VA; VT; WI; WV; ON
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AR; CO; IL; KS; MI; MN; MO; NE; NM; OK; SD; TX; WI
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Discussion | 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.) |
Oenothera rhombipetala is primarily a central plains species that has scattered localities in the Midwest to Illinois, Michigan, and Wisconsin, and barely entering the easternmost parts of Colorado and New Mexico. Oenothera rhombipetala had a broader delimitation (P. A. Munz 1965) until W. Dietrich and W. L. Wagner (1988) divided it into three species (O. clelandii, O. curtissii, and O. rhombipetala), with both of the split-off species being PTH. Evidence gathered by Dietrich and Wagner showed that these PTH species are geographically separated populations of small-flowered plants, and although they are very close morphologically, their distributions and morphological differences suggest that they were each derived independently from O. rhombipetala. Oenothera rhombipetala is self-incompatible. Oenothera pyramidalis H. Léveillé is a superfluous name and pertains here. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 10. | FNA vol. 10. |
Parent taxa | Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Kneiffia | Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Oenothera > subsect. Candela |
Sibling taxa | ||
Synonyms | Kneiffia fruticosa var. pilosella, K. pilosella, K. pratensis, K. sumstinei, O. fruticosa var. hirsuta, O. fruticosa var. pilosella, O. pratensis | O. heterophylla var. rhombipetala, O. leona, Raimannia rhombipetala |
Name authority | Rafinesque: Ann. Nat. 1: 15. (1820) | Nuttall ex Torrey & A. Gray: Fl. N. Amer. 1: 493. (1840) |
Web links |