Syst. Bot. 9: 129, fig. 1. 1984.
Herbs slender, rarely with aerenchyma when base submerged, forming slender, glabrate stolons 10–18 cm, 0.6–1.5 mm thick, occasionally bearing flowers and fruits. Stems erect, slightly ridged, usually well branched, (15–)35–90 cm, densely hirtellous. Leaves alternate; stipules lanceolate to broadly deltate, 0.2–0.5 × 0.1–0.3 mm; stolons: petiole 0.1–0.3 cm, blade elliptic to orbiculate, 1–1.8 × 0.6–1.4 cm, base attenuate, apex rounded to acute; stems: petiole narrowly winged, 0.1–0.8 cm, blade narrowly lanceolate-elliptic, 1.3–6.5 × 0.4–1.5 cm, base attenuate, margins entire with minute hydathodal glands, apex acute, surfaces densely hirtellous; bracts not much reduced. Inflorescences leafy racemes, flowers solitary in leaf axils; bracteoles attached near base of ovary, lanceolate or elliptic to narrowly so, (1.5–)2–4.3 ×0.3–0.9 mm, apex acuminate, surfaces hirtellous. Flowers: sepals ascending-spreading, green, broadly ovate-deltate, 1.5–3 × 1.4–2.1 mm, margins entire, apex acuminate, surfaces densely hirtellous; petals 0; filaments light green, 0.7–1.1 mm, anthers 0.3–0.4 × 0.4–0.5 mm; pollen shed in tetrads; ovary obovoid to obconic, 2.8–3.5 × 2–3 mm; nectary disc elevated 0.3–0.4 mm on ovary apex, light green, 1.4–2.5 mm diam., 4-lobed, glabrous; style light green, 0.3–0.5 mm, glabrous, stigma clavate to subcapitate, 0.4–0.6 × 0.3–0.5 mm, not exserted beyond anthers. Capsules oblong-obovoid, subterete to scarcely 4-angled, (3–)4–5(–5.3) × 2.5–3.5(–4) mm, hard-walled, irregularly dehiscent, pedicel 0.2–0.5 mm. Seeds light brown, elliptic-oblong with slightly curved ends, 0.5–0.7 ×0.3–0.4 mm, surface cells elongate transversely to seed length. 2n = 32.
Phenology: Flowering Jul–Sep.
Habitat: Wet, peaty habitats, ditches, margins of ponds, bogs, swamps.
Elevation: 0–100 m.
Fla., N.C., S.C., Va.
Ludwigia ravenii is an uncommon species occurring in scattered populations in coastal southeastern Virginia and eastern North Carolina, with single disjunct populations in southeastern South Carolina and northeastern Florida. C. I. Peng (1989) observed its similarity to L. pilosa by virtue of its dense, hirtellous pubescence, but noted its smaller, more consistently autogamous flowers. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.