Lavauxia lobata A. Nelson; L. primiveris (A. Gray) Small; Oenothera bufonis M. E. Jones; O. cespitosa Nuttall var. primiveris (A. Gray) H. Léveillé; O. johnsonii Parry; O. primiveris subsp. bufonis (M. E. Jones) Munz; O. primiveris var. bufonis (M. E. Jones) Cronquist; O. primiveris subsp. caulescens (Munz) Munz; O. primiveris var. caulescens Munz; Pachylophus johnsonii (Parry) Rydberg

Herbs winter-annual, caulescent to short-caulescent, long-hirsute, hairs often with reddish purple pustulate bases, especially proximally, also moderately strigillose, and glandular puberulent distally, often on leaves; from a weakly fleshy taproot. Stems (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. Leaves 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. Flowers 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. Capsules 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. Seeds 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. 2n = 14.

Flowering Feb–May(–Jun). Sandy soil on flats, low hills and margins of sand dunes, along arroyos, road­sides, in desert scrub, grasslands and oak-grasslands; 30–1600 m; Ariz., Calif., Nev., N.Mex., Tex., Utah; Mexico (Baja California, Chihuahua, Sonora).

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 south of 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).