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spach's evening primrose

Habit Herbs perennial (short-lived or, sometimes, suffrutescent) or annual, glabrous or strigillose; from a stout taproot. Herbs annual, densely strigillose; from a sparsely branched taproot.
Stems

1–many, weakly decumbent to ascending or erect, unbranched to moderately branched, (10–)25–80 cm.

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

Leaves

1–9 × (0.1–)0.3–1 cm, sometimes fascicles of small leaves to 2 cm present in non-flowering axils;

petiole 0–0.6 cm;

blade linear to narrowly lanceolate or oblanceolate, often folded lengthwise, usually not much reduced distally, proximalmost leaves sometimes spatulate, base attenuate, margins subentire or serrulate or spinulose-serrate, apex acute.

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

opening at sunrise;

buds with free tips 0–4 mm;

floral tube 5–20 mm;

sepals 4–12 mm, midribs keeled;

petals yellow, fading orangish to purplish, 6–25 mm; antisepalous filaments 2–8 mm, antipetalous filaments 1–4 mm, anthers 2–7 mm, pollen 90–100% fertile;

style 9–30 mm, stigma sometimes blue-black, discoid to quadrangular, exserted beyond anthers.

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

10–35 × 1–2 mm, hard, dehiscent 1/2 their length, often tardily dehiscent throughout their length.

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

sessile.

Seeds

obovoid, 1–1.8 mm, sharply angled, apex truncate.

1 × 0.5 mm.

2n

= 14.

Oenothera capillifolia

Oenothera spachiana

Phenology Flowering Mar–May.
Habitat Prairies, open roadsides, sandy places.
Elevation 10–200 m. (0–700 ft.)
Distribution
c United States; sc United States; n Mexico
from FNA
AL; AR; LA; MS; OK; TX
[BONAP county map]
Discussion

Subspecies 2 (2 in the flora).

Oenothera capillifolia is self-incompatible (H. F. Towner 1977).

Oenothera berlandieri (Spach) Steudel 1841, not D. Dietrich 1840, is superfluous and cannot be used in Oenothera when transferred from Calylophus, and pertains here.

(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.)

Key
1. Stems 1–several, ascending to erect, 30–80 cm; leaves 2.5–9 cm.
subsp. capillifolia
1. Stems several–many, decumbent to ascending, (10–)25–40 cm; leaves 1–4 cm.
subsp. berlandieri
Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Calylophus > subsect. Calylophus 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. 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. 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
Subordinate taxa
O. capillifolia subsp. berlandieri, O. capillifolia subsp. capillifolia
Synonyms Meriolix capillifolia Blennoderma drummondii, Kneiffia spachiana, O. uncinata
Name authority Scheele: Linnaea 21: 576. (1848) Torrey & A. Gray: Fl. N. Amer. 1: 498. (1840)
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