Glabrous perennial with several long, fleshy roots 0.5–1.3 cm thick; principal lvs cordate-ovate, mostly 12–25 × 8–20 cm, the main lateral veins not parallel to the margin, tending to arise from the proximal part of the midvein within the blade, scapes to 3 dm, stout and hollow; spikes to 3 dm, interrupted, the axis exposed; bracts and sep about equal, broadly round-ovate, nearly flat, with very narrow keel, herbaceous sides, and narrow scarious margins, obtuse or rounded at the tip; fr ovoid, 5–10 mm, circumscissile at or just below the middle; seeds 2(–4), 3–4 mm, smooth, mucilaginous; 2n=24. Semiaquatic, in marshes and along streams, especially on calcareous substrate; O. and s. Ont. to Wis. and Mo., and occasionally to N.Y., Va., N.C., Ga. and Ala.; now rare. Mainly spring.
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