Stems usually reddish purple, rarely yellow, slender. Inflores­cences: bracts ovate, membra­nous, margins entire, apex acute. Pedicels 0(–0.5) mm. Flowers 5-merous, 3–4(–4.5) mm, fleshy; papillae absent; calyx purplish or creamy white, campanulate, 1/2–2/3 corolla tube length, divided 1/2–2/3 its length, not evidently reticulate, ± shiny, lobes ovate-triangular, bases overlapping, margins entire, apex acute to acuminate; corolla usually white, sometimes pink or purple-tinged both fresh and dry, campanulate-cylindric, 2.8–4 mm, not saccate, tube 1.5–3 mm, lobes spreading, usually triangular, some­times lanceolate, 1/2–3/4 corolla tube length, margins entire, apex acute to acuminate, straight; infrastaminal scales oblong-spatulate, 1.1–2 mm, 4/5 corolla tube length, bridged at 0.4–0.6 mm, base rounded, uniformly short-fimbriate, fimbriae 0.08–0.2 mm; stamens exserted, shorter than corolla lobes; filaments 0.4–0.7 mm; anthers 0.3–0.7 × 0.3–0.5 mm; styles terete; style plus stigmas 1.2–2.2 mm, ± equaling to 2 times ovary length; stigmas cylindric to terete, 0.6–1 mm, equaling style. Capsules globose, 1.6–2.2 × 1.6–2.3 mm, not thickened or raised around interstylar aperture, translucent, capped by withered corolla. Seeds 2–4, angled, subglobose to ovoid, 0.8–1.1 × 0.7–1 mm, hilum region terminal. 2n = 14.

Flowering Jul–Oct. Hosts: herbs, especially Medicago, Trifolium, and other legumes; 0–2000 m; introduced; B.C., N.B., N.S., Ont.; Calif., Conn., Idaho, Iowa, Ky., Maine, Md., Mass., Mich., Mo., Mont., Nebr., Nev., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Vt., Va., Wash., W.Va., Wyo.; Europe; introduced also in Mexico, South America, Asia, s Africa, Australia.

Ephemeral occurrences of var. epithymum are associated with contaminated seeds of forage legume crops.