Ludwigia sphaerocarpa

Herbs often with prominent aerenchyma when base submerged, forming stolons 20–90 cm, 2–3.5 mm thick, floating, sometimes branched. Stems erect, slightly ridged, well branched, (40–) 60–110 cm, densely strigillose or glabrous. Leaves alternate; stipules lanceolate-deltate, 0.1–0.4 × 0.1–0.2 mm; stolons: petiole ± winged, 0.1–0.3 cm, blade narrowly elliptic to oblanceolate or spatulate, 0.9–3 × 0.4–0.8 (–1.3) cm, base attenuate, margins subentire with hydathodal glands, apex acute or obtuse; stems: petiole 0.1–0.4 (–1) cm, blade narrowly elliptic or lanceolate to sublinear, on main-stem (2.6–) 6–10 × 0.5–1.1 (–1.6) cm, on branches 2–5 (–6) × 0.3–0.5 (–0.6) cm, base attenuate or narrowly cuneate, margins entire with hydathodal glands mainly on primary cauline leaves, apex acute to very narrowly acute, surfaces glabrous or densely strigillose; bracts not much reduced. Inflorescences open, leafy racemes, more congested on branches, flowers solitary in leaf-axils; bracteoles attached in subopposite pairs near base of ovary, usually linear to very narrowly lanceolate, rarely lanceolate, 0.5–1.5 × 0.1–0.3 mm, apex acuminate. Flowers: sepals ascending, yellow or cream adaxially, ovate-deltate, 2–3.5 (–4) × 1.6–3 (–3.3) mm, margins entire, apex acuminate, surfaces glabrous or densely strigillose; petals 0; filaments yellow, 1–1.7 mm, slightly dilated toward base, anthers 0.5–0.8 × 0.4–0.7 mm; pollen shed in tetrads; ovary broadly obovoid or cupshaped, 1.5–3.5 × 2–3 mm; nectary disc elevated 0.4–0.6 mm on ovary apex, bright-yellow, 1.5–3 mm diam., 4-lobed, glabrous or short-hirtellous between lobes; style yellow, 0.6–1 (–1.3) mm, glabrous or strigillose proximally, stigma yellow, capitate to subglobose, 0.3–0.5 × 0.4–0.7 mm, not exserted beyond anthers. Capsules sometimes tinged pink, subglobose, subterete, 2–4 (–4.5) × 2–4 mm, hard-walled, irregularly dehiscent, pedicel 0.5–1.2 (–2.3) mm. Seeds brown to light-brown, elliptic, 0.4–0.7 × 0.3–0.4 mm, surface cells transversely elongate to seed length, sometimes oblique. 2n = 32.

Phenology: Flowering Jun–Sep.
Habitat: Drainage ditches, shores of slow-moving streams or ponds, marshes, swales, swamp forests, edges of limestone sinks, peaty bogs in pastures, interdunal marshes.
Elevation: 0–300 m.

Ala., Conn., Del., Fla., Ga., Ill., Ind., La., Md., Mass., Mich., Miss., N.J., N.Y., N.C., Pa., R.I., S.C., Tenn., Tex., Va.

Discussion

Ludwigia sphaerocarpa has its primary distribution along the Atlantic coastal plain, from Massachusetts to north-central Florida, and west along the Gulf coastal plain sporadically to southeastern Texas. Disjunct populations occur in south-central Tennessee, extreme southwestern Indiana, along Lake Michigan in northeastern Illinois and northwestern Indiana, and in west-central New York. In Michigan, L. sphaerocarpa is known from Allegan and Berrien counties, as reported by Reznicek and Voss in the Michigan Flora (https://michiganflora.net/species.aspx?id=1757).

Selected References

None.

Lower Taxa