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FNA | Family List | FNA Vol. 10 | Onagraceae | Oenothera

75. Oenothera nutans G. F. Atkinson & Bartlett, Rhodora. 15: 83. 1913.

Oenothera austromontana (Munz) P. H. Raven, W. Dietrich & Stubbe; O. biennis Linnaeus subsp. austromontana Munz; O. biennis var. austromontana (Munz) Cronquist; O. biennis var. nutans (G. F. Atkinson & Bartlett) Wiegand

Herbs biennial, often appearing glabrous to naked eye, usually strigillose and sparsely to moderately villous proximal to inflorescence, hairs translucent and with or without pustules, pustules not red (in fresh material), inflorescence glabrous, glandular puberulent, or strigillose and glandular puberulent. Stems erect, red on proximal parts, green on distal ones, rarely red throughout, unbranched or with branches obliquely arising from rosette and secondary branches arising from main stem, 30–200 cm. Leaves in a basal rosette and cauline, basal 10–32 × 3–7 cm, cauline 6–20 × 2–8 cm; blade green to pale green, narrowly oblanceolate to narrowly obovate, or narrowly elliptic, sometimes lanceolate distally, margins usually flat, rarely undulate, bluntly dentate, teeth widely spaced, sometimes sinuate-dentate proximally; bracts caducous. Inflorescences erect, unbranched or with secondary branches just proximal to main one. Flowers opening near sunset; buds erect, 4–6 mm diam., with free tips terminal, erect, 1.5–6 mm; floral tube 30–43 mm; sepals yellowish green or flushed with red, 10–23 mm; petals yellow to pale yellow, fading pale yellowish white, very broadly obcordate, 14–25(–30) mm; filaments 10–25 mm, anthers 4–10 mm, pollen ca. 50% fertile; style 35–63 mm, stigma surrounded by anthers at anthesis. Capsules erect or slightly spreading, dull green when dry, narrowly lanceoloid to narrowly ovoid, 12–36 × 3–6 mm, free tips of valves 1–1.5 mm. Seeds 1–1.9 × 0.6–0.9 mm. 2n = 14.

Flowering Jun–Aug(–Sep). Open, often disturbed sites, stream beds, flood plains, slopes, margins of mixed deciduous forests, roadsides, old fields; (200–)400–1700 m; Ont.; Ala., Ark., Conn., Del., Fla., Ga., Ind., Ky., Maine, Md., Mass., Mich., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Vt., Va., W.Va.

Oenothera nutans is a PTH species and forms a ring of 14 chromosomes or a ring of 12 and 1 bivalent in meiosis, and is self-compatible and autogamous (W. Dietrich et al. 1997). It has plastome III and a BB genome composition. The disjunct occurrences of O. nutans in Arkansas and Missouri probably represent unintentional introductions by humans.


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