Oenothera flava
Oenothera primiveris
long-tubed evening primrose, yellow evening primrose
desert evening primrose, yellow desert evening primrose
(when present) ascending, 1–several, usually densely leafy, 0–2 cm.
(when present) unbranched and erect or, sometimes, few branches from near base, in robust plants stems and caudex hollow and greatly enlarged, especially toward base, densely leafy, 5–35 cm.
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.
in a basal rosette, sometimes also cauline, (1.4–)6–15(–28) × (0.2–)1–3.5(–5.6) cm;
petiole (0.9–)3.5–8(–14) cm;
blade oblanceolate to linear-oblanceolate, pinnatifid or 2-pinnatifid to shallowly pinnately lobed, margins sinuate-dentate or subentire, apex obtuse.
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.
usually 1–4, rarely more, opening per day, 1–2 hours before sunset;
sepals (7–)12–25(–30) mm;
petals yellow, fading reddish orange to purple, obcordate to obovate, (6–)13–35(–40) mm;
filaments 6–16 mm, anthers 3–10 mm;
style (32–)40–90(–100) mm, stigma exserted beyond anthers or surrounded by them.
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.
woody in age, sigmoid or curved to nearly straight, lanceoloid to ovoid, 4-angled, 10–45(–60) × 4–8 mm, beak 4–15 mm, dehiscent 1/4–2/3 their length;
sessile.
asymmetrically cuneiform, 1.8–2.2(–2.6) mm.2n = 14.
usually numerous, in 2 rows per locule, obovoid to oblanceoloid, 3–3.5 × 1–1.4 mm, surface thickened above raphe and at distal end into U-shaped structure.
= 14.
Oenothera flava
Oenothera primiveris
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.)
Oenothera primiveris has a complex variation pattern (W. L. Wagner 2005). In the western part of the range from southeastern California across southern Nevada to southern Utah counties of Emery, Kane, and Washington, and northwestern Mohave County, Arizona, plants generally have a gray appearance, with dense pubescence and larger flowers with widespread self-compatibility, but with scattered populations retaining self-incompatibility. Populations from southof the Mogollon Plateau to southern New Mexico, western Texas, Chihuahua, Sonora, and Baja California, Mexico, are greener in appearance with smaller to much smaller flowers, and are all self-compatible with occasional outcrossing or complete autogamy. The transitions between these two extremes are so extensive and more or less gradual that it is not possible to subdivide into two subspecies as has been done previously (Wagner).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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