Oenothera cespitosa var. navajoensis (W. L. Wagner, Stockhouse & W. M. Klein) Cronquist; Pachylophus caulescens Rydberg

Herbs caulescent or acaulescent, moderately to densely crinkly-villous (often appearing shaggy), and glandular puberulent. Stems (if present) unbranched to few-branched, (0–)10–25 cm. Leaves (3.5–)4–13(–16) × (0.7–)1–3.2 cm; petiole (1.3–)1.7–10(–12) cm; blade oblanceolate to rhombic-obovate, margins often coarsely and irregularly dentate or serrate, sometimes pinnately lobed, often with several larger lobes near blade base. Flowers: buds often recurved when young; floral tube (35–)40–70(–80) mm; sepals 22–27(–32) mm; petals fading pink to light rose, (25–)28–32(–34) mm; filaments 11–15(–17) mm, anthers 9–12 mm; style (50–)59–85(–96) mm. Capsules straight, oblong-lanceoloid, base asymmetrical, 13–35(–40) × 5–6 mm; valve margins with a low sinuate ridge to 8–15 small, nearly distinct tubercles; pedicel 1–3 mm. Seeds narrowly obovoid, 2.1–2.6 × 1.1–1.3 mm, embryo 1/2 of seed volume, surface minutely papillose; seed collar forming a narrow slit above raphe with a slightly sunken membrane, mar­gin entire or obscurely sinuate distally. 2n = 14, 28.

Flowering (Apr–)May–Jun. Colorado Plateau region, forming small colonies on loose or compacted soil derived from clay, shale, fine-textured sandstone, or gypsum, on slopes and along small drainage patterns, often around harvester ant mounds, arroyos in somewhat sandy or gravelly soil, in shrubby commu­nities dominated by Atriplex confertifolia, A. corrugata, A. cuneata, Artemisia spinescens, Coleogyne ramosissima, Frankenia jamesii, Hilaria jamesii, with big sagebrush scrub or sage-grasslands, rarely in lower pinyon-juniper woodlands; 1100–1900(–2100) m; Ariz., Colo., N.Mex., Utah.