Blennoderma drummondii Spach; Kneiffia spachiana (Torrey & A. Gray) Small; Oenothera uncinata Scheele

Herbs annual, densely strig­illose; from a sparsely branched taproot. Stems erect, usually unbranched or with few ascend­ing branches, 10–30(–45) cm. Leaves in a basal rosette and cauline, basal 2–5 × 0.5–1.5 cm, petiole 0.5–2 cm, blade oblanceo­late to elliptic, margins subentire; cauline 3–6 × 0.2–0.6 cm, petiole 0.2–0.6(–1.5) cm, blade narrowly lanceolate to linear, margins subentire. Inflorescences erect, flowers in leaf axils in distal 1/2 of plant. Flowers opening near sunrise; buds with free tips to 1 mm, erect to spread­ing; floral tube 4–10 mm; sepals 4–8 mm; petals pale yellow, fading pale pink, 5–14 mm; filaments 3–7 mm, anthers 2–4 mm, pollen 85–100% fertile; style 3–7 mm, stigma surrounded by anthers. Capsules broadly clavate, 4-angled, 5–15 × 3–5 mm, stipe 2–5 mm; sessile. Seeds 1 × 0.5 mm. 2n = 14.

Flowering Mar–May. Prairies, open roadsides, sandy places; 10–200 m; Ala., Ark., La., Miss., Okla., Tex.

G. B. Straley (1977) determined Oenothera spachiana to be self-compatible and autogamous. Collections outside the native range of O. spachiana have been made as a ballast weed in Camden County, New Jersey.

Oenothera drummondii (Spach) Walpers (1843), not Hooker (1834) is a later homonym and pertains here.