Gaura villosa Torrey var. mckelveyae Munz, Bull. Torrey Bot. Club 65: 214. 1938; Gaura mckelveyae (Munz) P. H. Raven & D. P. Gregory

Herbs perennial, clumped, long-villous, more sparsely so distally, hairs erect, 2–4 mm, also strigillose, sometimes glabrate distally or also sparsely glandular puberulent; from twisted, woody rootstock. Stems ascending, branched below or just above ground, branched also proximal to inflorescences, 30–70(–120) cm. Leaves in a basal rosette and cauline, basal 3–17 × 0.8–2 cm, blade oblanceolate, cauline 1–6.5 × 0.1–1.5 cm, sessile, blade narrowly oblanceolate to elliptic, margins conspicu­ously sinuate-dentate, often undulate. Inflorescences slender. Flowers 4-merous, zygomorphic, opening near sunset; floral tube 2–3.5 mm; sepals 6–12 mm; petals white, fading dark pink to red, slightly unequal, elliptic-obovate, 7–11 mm, long-clawed; stamens presented in lower 1/2 of flower, filaments 5–9 mm, lanate at very base, anthers 2–4 mm, pollen 90–100% fertile; style 9–16 mm, stigma exserted beyond anthers at anthesis. Capsules reflexed, lanceoloid to narrowly ovoid, narrowly 4-winged, 8–19 × 1.5–2 mm, tapering to a sterile stipe 3–9 mm. Seeds (1 or)2–4, 2–3 × 1 mm, yellowish to reddish brown. 2n = 14.

Flowering Mar–Jun. Sandy soil; 0–300 m; Tex.; Mexico (Nuevo León, Tamaulipas).

Oenothera mckelveyae, on the Rio Grande Plain, is found in an area bounded by from Dimmit and LaSalle counties east to Karnes and Refugio counties in the north, southward through south Texas, extending to northeastern Tamaulipas and adjacent Nuevo León. P. H. Raven and D. P. Gregory (1972[1973]) found Oenothera mckelveyae to be self-incompatible.