Stems rarely reddish green, 10–55(–90) cm. Leaves: petiole 0–1 cm, blades linear-elliptic to linear, sometimes very narrowly elliptic, those on main axis 3–5(–7) × 0.3–0.5(–1) cm, those on branches 0.8–3.6 × 0.2–0.3(–0.8) cm. Inflorescences: brac-teoles attached at base of ovary, 0.4–0.8 × 0.1–0.2 mm. Flowers: sepals 1.1–1.9 × 1–1.8 mm, apex acute or short-acuminate; nectary disc obscurely, minutely papillose; style 0.4–0.8 mm, stigma 0.2–0.3 mm diam. Capsules obscurely 4-angled, 2–5 × 1.3–2 mm, pedicel 0–0.2 mm. Seeds 0.6–0.8 × 0.3–0.4 mm, surface cells elongate transversely to seed length.

Flowering Apr–Nov. Ditches, low meadows, coastal prairies, seeps in sandy woods, moist sinkholes in granite outcrops, old clay fields; 0–200 m; La., Okla., Tex.

Subspecies brachycarpa grows along the Gulf Coast from southwestern Louisiana to Nueces County, Texas, and more sporadically northward in eastern Texas to south-central Oklahoma.

Subspecies brachycarpa was published initially by Peng as a new combination based on Ludwigia cylindrica var. brachycarpa Torrey & A. Gray, not realizing that the variety was based on Jussiaea brachycarpa Lamarck, which Peng considered to be a synonym of L. glandulosa subsp. glandulosa. Therefore, subsp. brachycarpa is a new subspecies but was invalid when published by Peng since it was not accompanied by a Latin description in 1986; that situation has since been remedied.