Plants 2-40 cm. Leaves: blade 5-23 cm × 3-12 mm. Inflorescences: floral bracts 2, inconspicuous. Flowers pink to magenta, rarely white or bluish, gaping, large; sepals erect, narrowly oblanceolate to narrowly oblong, 20-55 × 3-9 mm; petals arcuate, 23-49 × 4-10 mm; lip obovate to oblong, arcuate to reflexed near middle, often obscurely 3-lobed, 19-35 ×10-19 mm; disc with crest of yellow lamellae and fleshy processes. Capsules erect, ovoid to ellipsoid, 15-25 mm. 2n = 40. Flowering Jun--Jul. Sphagnum bogs, coniferous swamps, calcareous treed to open fens, and moist, acid, sandy meadows; 0--1100 m; Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Sask.; Conn., Del., Ind., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., W.Va., Wis. The occurrence of Arethusa bulbosa in Cook County, Illinois (F. Swink and G. S. Wilhelm 1994), and in Maryland are unconfirmed.