Gulf Coast or marsh swallow-wort

Ceropegia palustris Pursh, Fl. Amer. Sept. 1: 184. 1813; Cynanchum angustifolium Persoon 1805, not P. angustifolius S. Watson 1889; C. palustre (Pursh) A. Heller; Funastrum angustifolium (Persoon) Liede & Meve; Lyonia palustris (Pursh) Small; Seutera angustifolia (Persoon) Fishbein & W. D. Stevens; S. palustris (Pursh) Vail

Leaves drooping, linear, 2–8 × 0.1–0.6 cm, fleshy, apex acute, base cuneate. Inflorescences 7–20-flowered; peduncles 1–5 cm. Pedicels 3–5 mm. Flowers: calyx lobes lanceolate, acute, 1–2.5 mm, ciliate, 1 colleter present adaxially at each sinus; corolla glabrous, tube ca. 0.5 mm, lobes spreading to reflexed distally, lance­olate to narrowly lanceolate, 3–4 mm, apex acute to attenuate; corona segments white, rectangular to oblong, 1.5–2 mm, apex 2-dentate to truncate; style apex 2-lobed; ovules ca. 20. Follicles 4–8.5 × 0.5–1 cm. Seeds 10–20, light brown, 5–6 × 4–5 mm, coma white, 2–3 cm.

Flowering (Feb–)Apr–Oct(–Nov); fruiting (Feb–)May–Nov. Salt marshes, coastal dunes and flats, coastal hammocks, edges of mangroves, roadsides; 0 m; Ala., Fla., Ga., La., Miss., N.C., S.C., Tex.; Mexico (Coahuila, Yucatán); West Indies; Central America (Belize).

Although Cynanchum angustifolium Persoon is the oldest basionym applicable to this species, the com­bination in Pattalias is precluded by P. angustifolius S. Watson, a synonym of Metastelma mexicanum. In the flora area, P. paluster is restricted to coastal strand, marshes, and estuaries, where it is quite likely to be the only milkweed vine present. Rarely, Orthosia scoparia may occur in close proximity, but that species has much smaller flowers and is commonly leafless.