Oenothera marginata Nuttall ex Hooker & Arnott, Bot. Beechey Voy., 342. 1839; Anogra longiflora A. Heller; O. cespitosa subsp. eximia (A. Gray) Munz; O. cespitosa var. eximia (A. Gray) Munz; O. cespitosa var. longiflora (A. Heller) Munz; O. cespitosa var. marginata (Nuttall ex Hooker & Arnott) Munz; O. eximia A. Gray; O. idahoensis Mulford; Pachylophus cylindrocarpus A. Nelson; P. exiguus (A. Gray) Rydberg; P. eximius (A. Gray) Rydberg; P. longiflorus (A. Heller) A. Heller; P. marginatus (Nuttall ex Hooker & Arnott) Rydberg; P. prolatus A. Nelson

Herbs caulescent or acaulescent, usually moderately to densely hirsute and glandular puberulent, rarely exclusively glandular puberulent. Stems usually unbranched, rarely with 1–several branches from near base, 10–40 cm. Leaves (2.8–)10–26(–36) × (0.6–)1–3(–4.5) cm; petiole (3–)4–11(–14) cm; blade usually oblanceolate to narrowly elliptic, rarely lanceolate, margins coarsely and irregularly pinnately lobed to dentate or, rarely, serrate. Flowers: floral tube (41–)80–140(–165) mm; sepals (22–)34–45(–54) mm; petals fading pink to lavender, (24–)35–50(–60) mm; fila­ments (16–)20–30(–35) mm, anthers (10–)12–17(–20) mm; style (78–)100–150(–185) mm. Capsules straight, cylindrical to, sometimes, lanceoloid-cylindrical, slightly asymmetrical, (21–)25–50(–68) × 6–8 mm, valve margins with minute to conspicuous tubercles, these sometimes coalesced into a sinuate ridge; pedicel (0–)1–40(–55) mm. Seeds usually narrowly to broadly obovoid, rarely suborbicular, 2.2–3.4 × 1.1–2.6 mm, embryo 1/5–1/2 of seed volume, surface appearing longitudinally striate, reticulate under magnification; seed collar large, usually appearing inflated, sealed by a flat membrane which is often slightly depressed into seed collar cavity, margin entire or obscurely sinuate distally. 2n = 14.

Flowering Mar–Aug. Rocky slopes, cracks in rocks, talus, along gravelly creek beds and arroyos, roadcuts in loose to somewhat compacted soil derived from granite, sandstone, limestone, volcanic cinder, rarely shale, mostly in foothill communities of pinyon-juniper woodlands, big sagebrush scrub, chaparral, grass­lands, openings in ponderosa pine forests; (400–)1200–2300(–3100) m; Ariz., Calif., Colo., Idaho, Nev., N.Mex., Oreg., Tex., Utah, Wash., Wyo.; Mexico (Chihuahua, Sonora).