Plants stout, (4-)10-30(-40) dm from long creeping rhizomes, wholly glabrous, or puberulent in the infl; lvs chiefly cauline, numerous, sessile or nearly so (the base of the blade often subauriculately rounded to a very short petiole), elliptic or lance-elliptic, ±serrate or the upper entire, not triple-nerved, not rugose, the larger ones 6-15 נ1.5-3.5 cm; infl paniculiform, sometimes conspicuously leafy-bracteate, with short or elongate, slightly to strongly recurved-secund branches; invol 4-6 mm, its bracts obtuse or rounded, the larger ones 0.7-1.2 mm wide; rays 6-10(-12); disk-fls 4-7; achenes short-hairy; 2n=18, 54. Fresh or brackish swamps near the coast; N.S.; Mass. to Fla.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.