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flaming Gorge evening primrose

fourpoint evening primrose

Habit Herbs perennial, subacaulescent or very short-caulescent, strigillose mostly along leaf margins and flower parts, also sparsely glandular puberulent, sometimes also sparsely hirsute distally; from a stout taproot, usually with several long, lateral roots often producing adventitious shoots. Herbs biennial, densely to sparsely strigillose, sometimes also sparsely glandular puberulent distally.
Stems

(when present) ascending, (1–)several–10, densely leafy, 1–2 cm.

sometimes with lateral branches arising obliquely from rosette, 30–100(–150) cm.

Leaves

primarily in a basal rosette, 7–14(–18) × (0.3–)0.5–1(–1.5) cm, moderately thick and stiff;

petiole (1.2–)3–5 cm;

blade linear to very narrowly elliptic, margins irregularly and coarsely dentate or pinnately lobed, apex long-attenuate.

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

dense, usually without lateral branches, mature buds usually not overtopping spike apex.

Flowers

1–3 opening per day near sunset;

buds with unequal free tips 1–3 mm;

floral tube (53–)60–100 mm;

sepals 26–50 mm;

petals bright yellow, fading deep reddish orange, drying purplish brown, 28–50 mm;

filaments 21–35 mm, anthers 9–11 mm;

style 75–143 mm, stigma exserted beyond anthers.

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

leathery in age, oblong-oblanceoloid, narrowly winged, wings oblong, 1–2(–4) mm wide, broadest near apex, 14–18(–22) × 7–8 mm (excluding wings), apex abruptly constricted, dehiscent 1/4–1/3 their length, valve surface with inconspicuous veins;

sessile.

narrowly lanceoloid, 13–25 × 2.5–3 mm.

Seeds

asymmetrically cuneiform, 2–2.5 mm.

brown, sometimes flecked with dark red spots, ellipsoid, 1–1.7 × 0.4–0.7 mm.

2n

= 14.

= 14.

Oenothera acutissima

Oenothera rhombipetala

Phenology Flowering May–Jun. Flowering May–Oct.
Habitat Restricted to sandy and gravelly, reddish, soil in seasonally wet sites, meadows, depressions, along arroyos, among rocks, in mixed conifer forests, sagebrush scrub. Fields, prairies, sandy soil.
Elevation 1800–2400(–2600) m. (5900–7900(–8500) ft.) 60–600(–1300) m. (200–2000(–4300) ft.)
Distribution
from FNA
CO; UT
[BONAP county map]
from FNA
AR; CO; IL; KS; MI; MN; MO; NE; NM; OK; SD; TX; WI
[WildflowerSearch map]
[BONAP county map]
Discussion

Oenothera acutissima is known only from the vicinity of Manila, eastern Uinta Mountains, Daggett and Duchesne counties, Utah, east to areas in and near the foothills of the Douglas and Blue mountains, in Uinta County, Utah, and Moffat County, Colorado.

(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. Lavauxia > subsect. Lavauxia Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Oenothera > subsect. Candela
Sibling taxa
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. 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. riparia, O. rosea, O. serrulata, O. sessilis, 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
Synonyms O. flava var. acutissima O. heterophylla var. rhombipetala, O. leona, Raimannia rhombipetala
Name authority W. L. Wagner: Syst. Bot. 6: 153, fig. 1. (1981) Nuttall ex Torrey & A. Gray: Fl. N. Amer. 1: 493. (1840)
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