Oenothera niveifolia Gandoger; O. sinuata Linnaeus var. humifusa (Nuttall) Torrey & A. Gray; Raimannia humifusa (Nuttall) Rose ex Britton & A. Brown

Herbs annual or short-lived perennial, densely strigillose, sometimes also villous, also becoming glandular puberulent distally. Stems erect to decumbent, much branched, 10–50(–90) cm. Leaves in a basal rosette and cauline, basal 4–8 × 0.7–1 cm, cauline 1–7 × 0.3–1.5 cm; blade usually grayish green, narrowly oblong to nar­rowly elliptic or narrowly obovate, margins remotely shallowly dentate to subentire; bracts spreading, flat. Flowers usually 1 opening per day near sunset; buds erect, with free tips erect and appressed or slightly spreading, 0.5–2 mm; floral tube 15–35 mm; sepals3–11 mm; petals yellow, very broadly obovate or obcordate, 4.5–16 mm; filaments 4–11 mm, anthers 2–5.5 mm, pollen ca. 50% fertile; style 23–45 mm, stigma surrounded by anthers at anthesis. Capsules cylindrical, sometimes slightly enlarged toward apex, 15–45 × 2–3 mm. Seeds usually ellipsoid to broadly ellipsoid, rarely subglobose, 1–2 × 0.5–0.9 mm. 2n = 14.

Flowering Apr–Nov. Dunes, open sandy places along or near Atlantic coast; 0–10 m; Ala., Del., Fla., Ga., La., Md., Miss., N.J., N.C., Pa., S.C., Va.; West Indies (Cuba); Bermuda.

Oenothera humifusa is a PTH species and forms a ring of 14 chromosomes in meiosis, and is self-compatible and autogamous (W. Dietrich and W. L. Wagner 1988). The inland collection from Iredell County, North Carolina, presumably represents an introduction. There are two geographically separated morphological forms of O. humifusa. Plants of one form are somewhat decumbent, with subentire cauline leaves and bracts; this form occurs in the southern part of the range. The other form is more upright, with more deeply divided leaves; it occurs from North Carolina northward.