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Howard's evening-primrose

long-tubed evening primrose, yellow evening primrose

Habit Herbs acaulescent or sometimes caulescent, moderately to densely strigillose and glandular puberulent, sometimes also sparsely to moderately hirsute; from a taproot, sometimes lateral roots producing adventitious shoots. Herbs perennial, rarely short-lived, acaulescent or very short-caulescent, glabrate to moderately strigillose, usually also glandular puberulent, sometimes sparsely hirsute distally; from a taproot.
Stems

(when present) ascending, longer ones becoming decumbent, leafy, sometimes densely so, 0–10(–30) cm.

(when present) ascending, 1–several, usually densely leafy, 0–2 cm.

Leaves

in a basal rosette, sometimes also cauline, (6–)8.5–17(–23) × (0.5–)1–2(–3) cm;

petiole 2–7.5 cm;

blade usually oblanceolate, elliptic to narrowly oblong, rarely lanceolate, margins often undulate, entire or remotely and irregularly pinnately lobed mostly in proximal 1/2, rarely more regularly pinnately lobed and lobing extending to distal 1/2, sinuses usually extending less than 1/2 to midrib, lobes triangular to oblong or linear, (1–)4–9(–13) mm, apex acute to obtuse.

primarily in a basal rosette, (3.4–)6–30(–36) × (0.5–)1.5–5(–7) cm, flexible, sometimes ± fleshy;

petiole (0.2–)2–7(–10) cm;

blade oblanceolate to linear, margins usually irregularly and coarsely pinnately lobed, rarely subentire, apex acute.

Flowers

usually 1 or 2, rarely more, opening per day near sunset, strongly and sweetly scented;

buds with unequal free tips 1–3(–4) mm;

floral tube (43–)60–110(–125) mm;

sepals (30–)35–60(–80) mm;

petals brilliant yellow, fading deep red, drying deep reddish purple to reddish brown, usually broadly obovate, rarely subrhombic, (30–)40–60(–73) mm, sometimes with a terminal tooth;

filaments (19–)25–38 mm, anthers 10–17 mm;

style(90–)110–145(–165) mm, stigma exserted beyond anthers at anthesis.

1–4 opening per day near sunset;

buds with free tips (1–)2–10(–12) mm;

floral tube (24–)40–200(–265) mm;

sepals (8–)11–40(–42) mm;

petals bright yellow, sometimes paler (in smaller-flowered plants), fading pale orange, drying purple, (7–)10–45(–50) mm;

filaments (5–)8–23(–26) mm, anthers (2–)3–13(–16) mm;

style (40–)50–250(–290) mm, stigma exserted beyond or surrounded by ring of anthers.

Capsules

leathery, ovoid, narrowly ovoid, or narrowly lanceoloid to broadly ellipsoid, winged, wings (2–)4–7(–11) mm wide, body (20–)25–50(–80) × 4–6 mm, dehiscent 1/4–1/3 their length;

pedicel 2–6 mm.

leathery in age, surface usually conspicuously reticulate, usually narrowly ovoid or ellipsoid, sometimes ovoid or lanceoloid, winged, wings narrowly oblong, (2–)3–5(–6) mm wide, confined to distal 2/3 of capsule, (10–)20–35(–43) × 4–8 mm (excluding wings), gradually constricted to a short beak, dehiscent 1/4–1/2 their length, valve surface usually conspicuously reticulate;

sessile.

Seeds

numerous, usually in 1 row per locule, rarely in 2 rows toward base, obovoid to subcuboid, 3–8 × 2.5–3.5 mm.

asymmetrically cuneiform, 1.8–2.2(–2.6) mm.2n = 14.

2n

= 28, 42, 56.

Oenothera howardii

Oenothera flava

Phenology Flowering May–Jul. Flowering Mar–Aug(–Oct).
Habitat Open or rocky areas, in shale, fine-textured sandstones, clays, gypsum, or limestone from High Plains grasslands, open sites in pinyon-juniper woodlands, ponderosa pine-Douglas fir forests. Local and colonial, sometimes abundant in wet (at least seasonally moist) clay to gravelly sand of swales, desiccating flats and ponds, montane meadows, margins of permanent or seasonal watercourses, open sites.
Elevation (1000–)1500–2300(–3000) m. ((3300–)4900–7500(–9800) ft.) 300–3200 m. (1000–10500 ft.)
Distribution
from FNA
CO; KS; NV; UT; WY
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[BONAP county map]
from FNA
AZ; CA; CO; ID; MT; ND; NE; NM; NV; OR; SD; UT; WA; WY; AB; MB; SK; Mexico (Chihuahua, Durango, Guanajuato, Hidalgo, Jalisco, Sonora)
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[BONAP county map]
Discussion

Oenotherahowardii is known from three disjunct areas: three collections on the High Plains (Baca and Otero counties, Colorado, and Hamilton County, Kansas); open yucca-juniper grassland, rocky slopes or disturbed areas on shale substrates along the Colorado counties of Boulder, Denver, Jefferson, and Larimer, and just over the state line in Wyoming; and, common to scattered, mostly on rocky slopes but also in shaded canyon sites on fine-textured red sandstones, clays, gypsum, chalky white degraded limestone or limestone in pinyon-juniper woodland to ponderosa pine-Douglas fir forest in southern Utah and eastern Nevada.

A. Nelson intended to publish Lavauxia howardii as a new combination and base it on Oenothera howardii M. E. Jones (1893), which was not validly published at the time, but inadvertently published L. howardii as a new species. Oenothera howardii (A. Nelson) W. L. Wagner is an isonym.

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

Petals in Oenothera flava typically range from 7–32 mm with floral tubes 24–100 mm; however, plants from three disjunct areas: the Mogollon Plateau in Arizona to Catron County, New Mexico; Sacramento Mountains and Sierra Blanca, Lincoln and Otero counties, New Mexico; and the Sierra Madre Occidental from northern Chihuahua south to Durango, have much larger petals (30–55 mm) and longer floral tubes (80–265 mm). They were originally recognized as a distinct species or most recently as a subspecies (O. flava subsp. taraxacoides), but detailed study of the variation pattern suggests that the larger flowers occur in areas of high hawkmoth species diversity and higher rates of outcrossing, similar to the pattern discussed in detail by D. P. Gregory (1963, 1964). R. A. Raguso et al. (2007) and H. E. Summers et al. (2015) came to the same conclusion in an independent study of floral biology of sect. Lavauxia. Because populations from the three disjunct areas appear to have diverged independently from lower-elevation source populations, it seems best to treat the complex as one variable species without any formal subdivision.

(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. Megapterium Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Lavauxia > subsect. Lavauxia
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. 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. 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
Synonyms Lavauxiahowardii a. Lavauxiaflava a., L. palustris, L. taraxacoides, O. flava subsp. taraxacoides, O. murdockii, O. taraxacoides, O. triloba var. ecristata
Name authority (A. Nelson) M. E. Jones ex Prain in B. D. Jackson et al.: Index Kew., suppl. 3: 121. (1908) — (as howardi) (A. Nelson) Garrett: Spring Fl. Wasatch ed. 4, 106. (1927)
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