Fl. ech. 94. 1819.
Plants annual or short-lived perennial, delicate, 4–25 cm, stipitate-glandular in inflorescence. Taproots slender to ± stout. Stems erect to ascending or prostrate, usually much-branched proximally; main stem 0.3–0.5 mm diam. proximally. Leaves: stipules conspicuous, shiny white, lanceolate, 3.5–5 mm, apex long-acuminate; blade filiform to linear, 0.4–1.5 cm, scarcely fleshy, apex apiculate to spine-tipped; axillary leaves 2–4+ per cluster. Cymes simple to 3+-compound or flowers solitary and axillary. Pedicels ascending to reflexed. Flowers: sepals connate 0.5–0.7 mm proximally, lobes often 3-veined, lanceolate, (2–)2.5–3.2 mm, to 4 mm in fruit, margins 0.1–0.3 mm wide, apex obtuse to acute; petals pink, obovate to ovate, 0.9–1 times as long as sepals; stamens 6–10; styles 0.6–0.8 mm. Capsules greenish to tan, 3.5–5 mm, 1–1.2 times as long as sepals. Seeds red-brown to dark brown, with submarginal groove, broadly ovate or ± truncate, angular at broad end, plump, 0.4–0.6 mm, sculpturing of parallel, wavy lines, margins with peglike papillae (30×); wing absent. 2n = 18, 27, 36, 54 (all Europe).
Phenology: Flowering spring–fall.
Habitat: Open forests, gravelly glades, meadows, mud flats, roadsides, disturbed places
Elevation: 0-2400 m
Introduced; St. Pierre and Miquelon, B.C., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Yukon, Alaska, Calif., Colo., Conn., Del., D.C., Idaho, Ill., Ind., Ky., Maine, Md., Mass., Mich., Minn., Mont., Nev., N.H., N.J., N.Mex., N.Y., Ohio, Oreg., Pa., R.I., Utah, Vt., Va., Wash., Wis., Wyo., Europe, Asia, introduced in South America, Australia.
Spergularia rubra was collected in 1901 on ballast in Alabama (Mohr, DS), the only record in the southeastern United States. It is the most widely distributed Spergularia species found outside of saline areas in the flora and has been in North America since at least the 1860s.