Stems erect, simple to branched distally, 4-10 dm, usually glabrous (rarely stipitate-glandular at nodes); rhizomes slender to thickened; bulblets absent. Leaves whorled or opposite; petiole absent or 0.1-3 cm, eciliate; blade elliptic to lanceolate or ovate, 4-8 × 1.5-2.5 cm, base cuneate, decurrent, margins entire, slightly revolute, eciliolate, apex acute to acuminate, surfaces punctate, glabrous; venation single-veined to obscurely pinnate. Inflorescences terminal, racemes (sometimes leafy), 20-35 cm. Pedicels 1.5-3 cm, glabrous or sparsely stipitate-glandular. Flowers: sepals 5, calyx streaked with black resin canals, 3-7 mm, stipitate-glandular, especially near margins, lobes lanceolate, margins thin; petals 5, corolla yellow, streaked with reddish or reddish-black resin canals, rotate, 5-8 mm, lobes with margins entire, apex rounded to obtuse, stipitate-glandular abaxially; filaments connate 1.7-3 mm, shorter than corolla; staminodes absent. Capsules 3-5 mm, dark-punctate, glabrous. 2n = 84. Flowering summer. Moist, open woods, swamp and pond margins, wet, sandy fields; 0-1500 m; Ont., Que.; Conn., Del., D.C., Ill., Ind., Ky., Maine, Md., Mass., Mich., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis. Lysimachia ×producta is a fertile hybrid between L. quadrifolia and L. terrestris, occurring as isolated populations or with one or both parents present.