Stems erect, simple, 3-8 dm, pubescent distally; rhizomes stout; bulblets absent. Leaves opposite to subopposite or whorled; petiole absent or 0.1-0.2(-0.4) cm, eciliate; blade lanceolate or linear-lanceolate to elliptic, 5-16 × 0.5-6 cm, base truncate to rounded or cuneate, not decurrent, margins entire, plane, eciliolate, apex acute to obtuse, surfaces punctate, glabrous or sometimes sparsely pubescent abaxially; venation pinnate. Inflorescences axillary, racemes, 1-3 cm. Pedicels 0.1-0.4 cm, stipitate-glandular or pubescent. Flowers: sepals 5-7(-9), calyx streaked with dark resin canals, 1-2.8 mm, glabrous, lobes narrowly lanceolate, margins thin; petals 5-7(-9), corolla light yellow, streaked with black or reddish-brown resin canals, somewhat funnelform, 3-7 mm, lobes with margins entire, apex rounded to acuminate, eglandular; filaments distinct or connate ca. 0.2 mm, nearly 2 times as long as corolla; staminodes absent (rarely staminodelike minute teeth present between fertile filaments). Capsules 2-3 mm, dark-punctate, glabrous. 2n = 40, 42, 54. Flowering spring-summer. Bogs, swamps, marshes, wet woods; 0-2000 m; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kans., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., N.H., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Utah, Vt., Wash., W.Va., Wis., Wyo.; Eurasia. Lysimachia thyrsiflora is known to hybridize readily with 17. L. terrestris (see discussion under the latter).
