Plants 3-25 cm, glabrous except pedicels rarely stipitate-glandular. Stems prostrate or decumbent, widely branched. Stipules 1-2.8 mm. Sepals 2.2-3.2 mm, to 4.5 mm in fruit, apex broadly rounded or blunt. Capsules 3.6-5.2 mm, 1.5-2 times as long as sepals. Seeds 0.9-1.4 mm. 2n = 36.

Flowering summer. Coastal salt marshes, brackish river margins, moist beach sand; 0-50 m; St. Pierre and Miquelon; N.B., Nfld. and Labr. (Nfld.), N.S., Nunavut, Ont., P.E.I., Que.; Conn., Maine, Mass., N.H., N.Y., R.I.