Herbs with aerenchyma when base submerged, forming sto­lons from lower nodes, 8–65(–95) cm, 0.7–2.5 mm thick. Stems erect or somewhat sprawling, slightly to distinctly winged (wings to 1.8 mm wide), branched distally, 40–120(–160) cm, glabrous. Leaves alternate; stipules ovate-deltate, often narrowly so, 0.2–0.4 × 0.1–0.3 mm, succulent; stolons: petiole 0.15–1 cm, blades orbic­ulate to oblanceolate or broadly elliptic, 0.4–2.6 × 0.4–1.5 cm, base attenuate, apex rounded to subacute; stems: petiole 0–0.3 cm, blade lanceolate-elliptic or very narrowly elliptic to linear, sometimes to oblanceolate or oblanceolate-elliptic near base, 1.8–10 × 0.2–1.3(–2) cm, base narrowly cuneate or attenuate, margins subentire with remote hydathodal glands, rarely minutely papillose-serrulate near apex, apex acute to narrowly acute, leaves on side branches much reduced; bracts much reduced. Inflorescences sometimes congested, leafy spikes or racemes, flowers solitary in distal leaf axils; bracteoles attached near base of ovary, lanceolate-elliptic or narrowly so, 2.4–4.7 × 0.6–1.5 mm, margins minutely papillose or smooth, apex acute, surfaces glabrous. Flowers: sepals spreading to reflexed, creamy white adaxially, broadly ovate-deltate, 2–4 × 1.6–4 mm, margins smooth or minutely papillose-serrulate, apex acute or acuminate, surfaces glabrous; petals 0; filaments nearly translucent, 1.1–1.7 mm, slightly dilated near base, anthers 0.5–0.9 × 0.4–0.7 mm; pollen shed singly; ovary obpyramidal, sharply 4-angled, 2–3.8 × 2–3.5 mm; nectary disc elevated 0.5–0.8 mm on ovary apex, bright yellow, square with rounded corners, 2–3.3 mm diam., prominently 4-lobed, glabrous; style pale green, 0.8–1.3 mm, glabrous, stigma pale yellow, subglobose, 0.3–0.6 × 0.3–0.7 mm, shallowly 4-lobed on top, not exserted beyond anthers. Capsules obpyramidal, sharply 4-angled and 4-winged, 3–5 × 2.8–4.5 mm, with hard walls somewhat bulging, dehiscent by apical ring, pedicel 0–0.8 mm. Seeds light brown, ellipsoid, slightly curved on both ends, 0.6–0.7 × 0.3–0.4 mm, surface cells elongate transversely to seed length. 2n = 48.

Phenology: Flowering Jun–Oct.
Habitat: Ditches, edges of ponds and lagoons, peaty or sandy swales, open cypress swamps, sandy borrow pits in open pine woods, swampy, flat outcrops of oolitic rocks, wet savannas, tidal flats, brackish marshes, sandy beach strands and hammocks.
Elevation: 0–50 m.

Distribution

• Generated Map
• Legacy Map

Ala., Fla., Ga., La., Miss., N.C., S.C., Va., West Indies (Jamaica).

Discussion

Ludwigia alata occurs only at very low elevations along the Atlantic and Gulf coastal plains from Virginia to the tip of Florida, and west to southwestern Louisi­ana, with disjunct populations on Jamaica (C. I. Peng 1989). This hexaploid species is often confused with L. lanceolata, with which it shares two genomes (Peng 1988, 1989) and with which it is frequently sympatric. The showy petals of L. alata suggest a higher level of outcrossing, and numerous natural hybrids have been docu­mented (Peng 1988, 1989).

Selected References

None.

Lower Taxa

None.