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fourwing evening-primrose

Habit Herbs perennial, densely strigillose, glabrate proximally; from fibrous roots. Herbs annual or perennial, strigillose and also hirsute; from a slender taproot.
Stems

ascending, unbranched to few-branched, 30–65 cm.

15–50 cm.

Leaves

in a basal rosette and cauline, basal 2.5–7 ×0.7–2.3 cm, petiole 1–1.5 cm, blade oblanceolate, margins subentire, undulate;

cauline (3–)6–7(–9) ×(0.3–)0.6–0.8(–1.1) cm, sessile, blade lanceolate to narrowly lanceolate, margins subentire.

2.5–10 × 0.6–2.5 cm;

petiole 0.2–2.2 cm;

blade usually lanceolate to oblanceolate, sometimes elliptic, margins weakly serrate to sinuate-pinnatifid.

Inflorescences

nodding, flowers in axils of distalmost few nodes.

Flowers

opening near sunrise;

buds with free tips 1–2 mm, connivent to spreading;

floral tube 10–15(–20) mm;

sepals 10–18 mm;

petals bright yellow, fading pale pink, 15–25 mm;

filaments 7–9 mm, anthers 5–8 mm, pollen 85–100% fertile;

style 10–12 mm, stigma exserted beyond anthers at anthesis.

1–3 opening per day near sunset;

buds with free tips 0.5–3 mm;

floral tube 10–30 mm;

sepals 20–40 mm;

petals white, fading pink, 20–43 mm;

filaments 12–18 mm, anthers 5–10 mm, pollen 85–100% fertile;

style 19–67 mm, stigma exserted beyond anthers at anthesis.

Capsules

ellipsoid, 4-angled, 8–10 × 3–4 mm, stipe 0–2 mm;

sessile.

broadly clavate or obovoid, 20–51 × 5–7 mm, winged, wings 2–4 mm, valve surface with prominent midrib, proximal stipe 8–45 mm;

sessile.

Seeds

1 × 0.5 mm.

narrowly obovoid, 1–1.5 × 0.5–0.7 mm.

2n

= 56.

= 14.

Oenothera sessilis

Oenothera tetraptera

Phenology Flowering May–Jun. Flowering Feb–May.
Habitat Moist remnant prairies in sandy or silty soil. Alluvial flats, open areas, sandy soil, weedy sites.
Elevation 0–100 m. (0–300 ft.) 10–300[–2000] m. (0–1000[–6600] ft.)
Distribution
from FNA
AR; LA; TX
from FNA
TX; Mexico; Central America; West Indies (Jamaica); n South America [Introduced widely in temperate Europe, Asia, s Africa, Australia]
[WildflowerSearch map]
[BONAP county map]
Discussion

Oenothera sessilis is relatively rare within its range and has a narrow overall distribution, occurring in Ashley, Phillips, Prairie, and St. Francis counties in Arkansas, Allen, Claiborne, and Tensas parishes in Louisiana, and Galveston County in Texas. Oenothera sessilis appears to be relatively rare and may no longer occur in Texas; it was last collected there in the 1840s by Lindheimer on Galveston Island. It is also rare in Louisiana but has been collected in recent decades. It is currently most common in Arkansas. P. A. Munz (1937, 1965) treated this taxon as O. sessilis, but G. B. Straley (1977) in his revision of sect. Kneiffia placed it as a subspecies of O. pilosella based on a common octoploid (2n = 56) chromosome number, morphology, and field studies. K. N. Krakos et al. (2014), based on new field studies, controlled greenhouse breeding experiments, and phylogenetic data found that this taxon differs morphologically from O. pilosella by having consistently shorter stature and smaller flowers, is self-compatible, and does not form a monophyletic group with O. pilosella in molecular analyses, and is here reinstated as a distinct species.

Oenothera sessilis is in the Center for Plant Conservation’s National Collection of Endangered Plants as O. pilosella subsp. sessilis.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

In the flora area, Oenothera tetraptera is known only from southern Texas. Oenothera tetraptera presumably has become naturalized in South America (Argentina, Bolivia, Colombia, Ecuador, Venezuela), West Indies (Jamaica), Europe, Asia, South Africa, and Australia.

Oenothera candida Dumont Courset is a superfluous name, as is O. candida Bellardi ex Colla, and they both pertain here. The name Hartmannia macrantha Spach is illegitimate 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. Leucocoryne
Sibling taxa
O. acutissima, O. albicaulis, O. argillicola, O. arida, O. arizonica, O. biennis, O. boquillensis, O. brachycarpa, O. calcicola, O. californica, O. canescens, O. capillifolia, O. cavernae, O. cespitosa, O. cinerea, O. clelandii, O. coloradensis, O. cordata, O. coronopifolia, O. coryi, O. curtiflora, O. curtissii, O. deltoides, O. demareei, O. dodgeniana, O. drummondii, O. elata, O. engelmannii, O. falfurriae, O. filiformis, O. filipes, O. flava, O. fruticosa, O. gaura, O. gayleana, O. glaucifolia, O. glazioviana, O. grandiflora, O. grandis, O. harringtonii, O. hartwegii, O. havardii, O. heterophylla, O. hispida, O. howardii, O. humifusa, O. jamesii, O. kunthiana, O. laciniata, O. lavandulifolia, O. lindheimeri, O. linifolia, O. longissima, O. macrocarpa, O. mckelveyae, O. mexicana, O. nealleyi, O. neomexicana, O. nutans, O. nuttallii, O. oakesiana, O. organensis, O. pallida, O. parviflora, O. patriciae, O. perennis, O. pilosella, O. platanorum, O. podocarpa, O. primiveris, O. psammophila, O. pubescens, O. rhombipetala, O. riparia, O. rosea, O. serrulata, O. simulans, O. sinuosa, O. spachiana, O. speciosa, O. stricta, O. suffrutescens, O. suffulta, O. tetraptera, O. texensis, O. toumeyi, O. triangulata, O. triloba, O. tubicula, O. villosa, O. wolfii, O. xylocarpa
O. acutissima, O. albicaulis, O. argillicola, O. arida, O. arizonica, O. biennis, O. boquillensis, O. brachycarpa, O. calcicola, O. californica, O. canescens, O. capillifolia, O. cavernae, O. cespitosa, O. cinerea, O. clelandii, O. coloradensis, O. cordata, O. coronopifolia, O. coryi, O. curtiflora, O. curtissii, O. deltoides, O. demareei, O. dodgeniana, O. drummondii, O. elata, O. engelmannii, O. falfurriae, O. filiformis, O. filipes, O. flava, O. fruticosa, O. gaura, O. gayleana, O. glaucifolia, O. glazioviana, O. grandiflora, O. grandis, O. harringtonii, O. hartwegii, O. havardii, O. heterophylla, O. hispida, O. howardii, O. humifusa, O. jamesii, O. kunthiana, O. laciniata, O. lavandulifolia, O. lindheimeri, O. linifolia, O. longissima, O. macrocarpa, O. mckelveyae, O. mexicana, O. nealleyi, O. neomexicana, O. nutans, O. nuttallii, O. oakesiana, O. organensis, O. pallida, O. parviflora, O. patriciae, O. perennis, O. pilosella, O. platanorum, O. podocarpa, O. primiveris, O. psammophila, O. pubescens, O. rhombipetala, O. riparia, O. rosea, O. serrulata, O. sessilis, O. simulans, O. sinuosa, O. spachiana, O. speciosa, O. stricta, O. suffrutescens, O. suffulta, O. texensis, O. toumeyi, O. triangulata, O. triloba, O. tubicula, O. villosa, O. wolfii, O. xylocarpa
Synonyms Kneiffia sessilis, O. pilosella subsp. sessilis, O. pilosella var. sessilis Hartmannia latiflora, H. tetraptera, O. latiflora, O. tetraptera var. immutabilis, Xylopleurum tetrapterum
Name authority (Pennell) Munz: Bull. Torrey Bot. Club 64: 291. (1937) Cavanilles: Icon. 3: 40, plate 279. (1796)
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