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threadleaf evening-primrose, threadleaf sundrop

spach's evening primrose

Habit Herbs annual, caulescent, strigillose or glabrous, also often glandular puberulent, especially distally; from a sparsely branched taproot. Herbs annual, densely strigillose; from a sparsely branched taproot.
Stems

unbranched or with many ascending branches arising near base, erect, 10–50 cm.

erect, usually unbranched or with few ascending branches, 10–30(–45) cm.

Leaves

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 2–5 × 0.5–1.5 cm, petiole 0.5–2 cm, blade oblanceolate to elliptic, margins subentire;

cauline 3–6 × 0.2–0.6 cm, petiole 0.2–0.6(–1.5) cm, blade narrowly lanceolate to linear, margins subentire.

Inflorescences

erect, flowers in leaf axils in distal 1/2 of plant.

Flowers

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 sunrise;

buds with free tips to 1 mm, erect to spreading;

floral tube 4–10 mm;

sepals 4–8 mm;

petals pale yellow, fading pale pink, 5–14 mm;

filaments 3–7 mm, anthers 2–4 mm, pollen 85–100% fertile;

style 3–7 mm, stigma surrounded by anthers.

Capsules

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.

broadly clavate, 4-angled, 5–15 × 3–5 mm, stipe 2–5 mm;

sessile.

Seeds

clustered in each locule, ovoid, surface minutely papillose, 1 × 0.5 mm.

1 × 0.5 mm.

2n

= 14.

= 14.

Oenothera linifolia

Oenothera spachiana

Phenology Flowering Apr–Jun(–Aug). Flowering Mar–May.
Habitat Prairies, open woodlands, open rocky and sandy sites, roadsides. Prairies, open roadsides, sandy places.
Elevation 0–400 m. (0–1300 ft.) 10–200 m. (0–700 ft.)
Distribution
from FNA
AL; AR; FL; GA; IL; KS; KY; LA; MO; MS; NC; OK; SC; TN; TX
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; LA; MS; OK; TX
[BONAP county map]
Discussion

Kneiffia linearifolia Spach (1835) is an illegitimate name based on Oenothera linifolia.

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

G. B. Straley (1977) determined Oenothera spachiana to be self-compatible and autogamous. Collections outside the native range of O. spachiana have been made as a ballast weed in Camden County, New Jersey.

Oenothera drummondii (Spach) Walpers (1843), not Hooker (1834) is a later homonym 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. Peniophyllum Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Kneiffia
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. 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. rhombipetala, O. riparia, O. rosea, O. serrulata, O. sessilis, O. simulans, O. sinuosa, 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 Kneiffia linifolia, O. linifolia var. glandulosa, Peniophyllum linifolium Blennoderma drummondii, Kneiffia spachiana, O. uncinata
Name authority Nuttall: J. Acad. Nat. Sci. Philadelphia 2: 120. (1821) Torrey & A. Gray: Fl. N. Amer. 1: 498. (1840)
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