Oenothera linifolia
Oenothera villosa
threadleaf evening-primrose, threadleaf sundrop
hairy evening-primrose, villous evening primrose, yellow evening-primrose
unbranched or with many ascending branches arising near base, erect, 10–50 cm.
erect, usually flushed with red proximally, sometimes green or red throughout, unbranched or with branches obliquely arising from rosette and secondary branches arising from main stem, 50–200 cm.
in a basal rosette and cauline, basal 1–2(–4) × 0.2–0.6 cm, petiole 0.2–1(–1.5) cm, blade ovate to obovate or narrowly elliptic;
cauline 1–4 × less than 0.1 cm, sessile, blade linear or filiform.
in a basal rosette and cauline, basal 10–30 × 1.2–4(–5) cm, cauline 5–20 × 1–2.5(–4) cm;
blade dull green or grayish green, narrowly oblanceolate, oblanceolate to narrowly elliptic, or narrowly lanceolate, margins flat or undulate, dentate to subentire, teeth sometimes widely spaced, sometimes sinuate-dentate proximally;
bracts persistent.
dense to open, erect, unbranched.
usually 1–3 opening per day near sunrise;
buds without free tips;
sepals 1.5–2 mm;
petals bright yellow, fading pink, obcordate to obovate, 3–5(–7) mm;
filaments 1–2 mm, anthers 0.5–1 mm;
style 1–2 mm, stigma surrounded by anthers at anthesis.
opening near sunset;
buds erect, 3–5 mm diam., with free tips terminal, erect, 0.5–3 mm;
floral tube 23–44 mm;
sepals green to yellowish green, red-striped, or flushed with red, 9–18 mm;
petals yellow to pale yellow, fading orange or pale yellow, very broadly obcordate, 7–20 mm;
filaments 7–15 mm, anthers 4–10 mm, pollen ca. 50% fertile;
style 30–55 mm, stigma surrounded by anthers at anthesis.
ellipsoid-rhombic to subglobose, 4-angled, 4–6(–10) × 1.5–3 mm, stipe 0–4 mm, valve midrib raised at distal end, indehiscent or tardily dehiscent distally;
sessile.
erect or slightly spreading, dull green or gray-green when dry, lanceoloid, 20–43 × 4–7 mm, free tips of valves 1–2 mm.
clustered in each locule, ovoid, surface minutely papillose, 1 × 0.5 mm.
1–2 × 0.5–1.2 mm.
= 14.
Oenothera linifolia
Oenothera villosa
Kneiffia linearifolia Spach (1835) is an illegitimate name based on Oenothera linifolia.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies 2 (2 in the flora).
Oenothera villosa is a PTH species and forms a ring of 14 chromosomes in meiosis, and is self-compatible and autogamous with plastome I and a AA genome composition (W. Dietrich et al. 1997). The original natural range of O. villosa was presumably from southern British Columbia south to California and east through the Rocky Mountain and the Great Plains regions. The wide occurrence east of this area in North America to eastern Quebec south throughout most of the eastern half of the United States, except for extreme southern and southeastern parts, is most likely the result of recent spread of this species, probably in the past several hundred years. Oenothera villosa is subdivided into two subspecies: subsp. strigosa occurs primarily in the Pacific Northwest southeast through the Rocky Mountains; subsp. villosa is found primarily from the eastern foothills of the Rocky Mountains eastward throughout the Great Plains region. Both taxa occur sporadically beyond these regions, and subsp. villosa is naturalized in many parts of the world.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Inflorescences usually dense (internodes in fruit usually shorter than capsule); plants dull green to grayish green, densely strigillose and sometimes also sparsely villous with appressed or subappressed hairs, these without or with red or green pustulate bases, rarely sparsely glandular puberulent distally; sepals green to yellowish green; leaf blade margins conspicuously dentate, venation prominent, especially abaxially. | subsp. villosa |
1. Inflorescences usually open (internodes in fruit usually as long as or longer than capsule); plants flushed with red at least proximally, often red throughout, strigillose, usually also villous with erect to sometimes appressed hairs with pustulate bases, pustules red, also glandular puberulent at least distally; sepals red-striped or flushed with red; leaf blade margins usually denticulate or subentire, sometimes moderately dentate, venation not prominent. | subsp. strigosa |
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