Flora of North America species comparison

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Oenothera riparia

Oenothera gayleana
Habit Herbs perennial, sparsely strigillose, becoming glabrate distally, usually also glandular puberulent distally; from a somewhat fleshy rootstock, forming adventitious roots where submerged. Herbs perennial, sometimes suffrutescent, usually strigillose, sometimes glabrous; from a stout taproot.
Stems

erect or ascending, usually many-branched throughout, proximal branches often somewhat spongy, 50–120 cm.

many, ascending to erect, branched from base, 15–30(–40) cm.
Leaves

in a basal rosette and cauline, softly succulent, 4–13.5 × 0.8–2.1 cm, petiole 0–1.5 cm, blade lanceolate to elliptic-lanceolate, margins remotely denticulate.

2.5–3.5 × 0.1–0.2 cm, rarely fascicles of small leaves present in non-flowering axils;

petiole 0–0.1 cm;

blade linear to narrowly linear-lanceolate, folded lengthwise, base long-attenuate, margins subentire or serrulate, apex acute.
Inflorescences

erect, flowers in axils of distalmost few nodes.

Flowers

opening near sunrise;

buds with free tips 0.5–2(–5) mm, erect to spreading;

floral tube 14–20 mm;

sepals 20–30 mm;

petals bright yellow, fading pale pink or lavender, 16–27 mm;

filaments 10–15 mm, anthers 7–8 mm, pollen 85–100% fertile;

style 15–30 mm, stigma exserted beyond anthers at anthesis.

opening near sunrise;

buds with free tips 0–0.5 mm;

floral tube 7 mm;

sepals 4–6 mm, midribs keeled;

petals yellow, fading yellow to orange, 15–20 mm; antisepalous filaments 5 mm, antipetalous filaments 2 mm, anthers 3–4 mm, pollen 90–100% fertile;

style 10 mm, stigma discoid to quadrangular, exserted beyond anthers at anthesis.
Capsules

oblong-clavate to oblong-ellipsoid, 4-angled or 4-winged, and wings 0.1–0.2 mm, 7–15 × 4–6 mm, stipe 2–5 mm;

sessile.

18–20 × 2 mm, hard, dehiscent 1/2 their length, often tardily dehiscent throughout their length.
Seeds

0.8 × 0.4 mm.

oblanceoloid, 1–1.8 mm, sharply angled, apex truncate.
2n

= 56.

= 14.

Oenothera riparia

Oenothera gayleana
Phenology Flowering May–Jul. Flowering May–Sep.
Habitat Isolated colonies in or at edge of water in marshes or slow-running rivers, apparently with at least some tidal influence. Gypsum outcrops.
Elevation 0–10 m. (0–0 ft.) 500–1400 m. (1600–4600 ft.)
Distribution
from FNA
GA; NC; SC; VA
from FNA
NM; TX
[BONAP county map]
Discussion

Oenothera riparia has not been accepted as a distinct species for a long time. The conservative approach used by G. B. Straley (1977) is here followed in recognizing a broadly delimited O. fruticosa, except that the very distinctive coastal tidal-freshwater semi-aquatic octoploid populations (Straley 1982) are recognized as O. riparia. Plants of these coastal populations, which occur from southern Virginia to North Carolina, are more robust, more branched, and less pubescent than those of the two subspecies of O. fruticosa, and have slightly succulent leaves and more prominent adventitious roots (Straley 1982; D. Boufford, pers. comm.). Further field studies and cytological analyses are needed to fully understand the geographical and ecological limits of O. riparia and confirm that it is strictly an octoploid species. K. N. Krakos et al. (2014) determined that Oenothera riparia is self-incompatible and is pollinated by bees (Bombus, Lassioglossum, Megachile, Parallelia, Xylocopa, and Zale).

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

Oenothera gayleana is a recently discovered gypsum endemic known only from scattered outcrops from De Baca and Eddy counties in New Mexico, and Culberson County in Texas. When published, the delimitation of O. gayleana included populations in Collinsworth and Dickens counties in the Texas panhandle, and adjacent Harmon County in Oklahoma. Subsequent study (B. Cooper et al., unpubl.) has determined they are actually O. serrulata.

(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. Calylophus > subsect. Calylophus
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. 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. 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
Synonyms Kneiffia riparia, O. tetragona var. riparia
Name authority Nuttall: Gen. N. Amer. Pl. 1: 247. (1818) B. L. Turner & M. J. Moore: Phytologia 96: 200, figs. 1, 2. (2014)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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