Long Beach primrose-willow

Ludwigiantha brevipes Long in N. L. Britton and A. Brown, Ill. Fl. N. U.S. ed. 2, 2: 586, fig. 3015. 1913

Herbs creeping and rooting at nodes, sometimes forming large mats. Stems prostrate, ascend­ing or erect at tips, terete, well branched, 20–70 cm, glabrous or, sometimes, minutely strigillose on leaf margins and inflorescence. Leaves opposite; stipules narrowly deltate, 0.05–0.15 × 0.05–0.1 mm; petiole narrowly winged, 0.2–0.8 cm, blades on submerged stems linear, 3.2–4.7 × 0.2–0.3 cm, those on emergent ones oblanceolate-elliptic to narrowly oblanceolate, (0.7–)1–1.7(–2) × 0.2–0.7(–1.1) cm, base very narrowly cuneate or attenuate, margins entire, apex acute; bracts not reduced. Inflorescences sometimes few-flowered, erect racemes, flowers paired in leaf axils of prostrate stems; bracteoles attached in opposite pairs at base of ovary or on pedicel distally, linear, 1–3(–4.5) × 0.1–0.7 mm, apex acuminate. Flowers: sepals slightly reflexed at anthesis, ascending in fruit, light green, ovate-deltate or narrowly so, (3.5–)4–5(–6) × 1.7–3 mm, with 3 parallel veins, margins strigillose and finely serrulate, apex narrowly acute to elongate-acuminate, surfaces glabrous; petals sometimes caducous, oblong-spatulate, 4.5–5.5 × 1.5–3 mm, base attenuate, apex obtuse; filaments spreading, pale cream, 1.8–2.5 mm, anthers 0.7–1 × 0.5–0.7 mm; pollen shed in very loose tetrads; ovary obconic-cylindric, subterete or scarcely 4-angled, 3–5 × 2–2.5 mm; nectary disc elevated 0.5–0.7 mm on ovary apex, bright yellow, 1.7–2.3 mm diam., 4-lobed, glabrate; style cream, 1.1–1.7 mm, stigma cream, broadly capitate, 0.4–0.6 × 0.5–0.8 mm, often exserted beyond spreading stamens. Capsules clavate, subterete to obscurely 4-angled, sometimes slightly curved, 6–10.5 × 2.5–4 mm, hard-walled, irregularly dehiscent, pedicel (4.5–)6–15(–20) mm. Seeds light to dark brown, ellipsoid, 0.6–0.7 × 0.3–0.5 mm, surface cells transversely elongate. 2n = 48.

Flowering Jun–Sep. Wet soil or sand along edges of ponds, lakes, marshes, or rivers, moist dune hollows, seasonal ponds; 0–200 m; Fla., N.J., N.C., S.C., Va.

The hexaploid Ludwigia brevipes is mainly re­stricted to the Atlantic coastal plain from central and eastern South Carolina to eastern North Carolina and extreme southeastern Virginia. The type collection of L. brevipes from middle New Jersey remains the only disjunct population north of the main range of this species more than 100 years after it was found. In 1988, an isolated population was found in the panhandle of Florida (Escambia County, Burkhalter 11065, MO) far to the southwest of the main range of L. brevipes; other reports of the species from Florida were erron­eous (C. I. Peng 1989).

Ludwigia brevipes is known to hybridize with L. palustris producing the sterile L. ×lacustris Eames.