Distribution: Eastern Washington and Oregon, east to Newfoundland and North Carolina.
Habitat: Ditches, ponds, and fresh-water marshes.
Flowers: June - July
Conservation Status: Imperiled in Washington (WANHP)
Strongly rhizomatous perennial, the culms 8-15 dm. tall, smooth and hollow.
Sheaths open, throat hairy only at the top; ligules 2-3 mm. long, composed chiefly of a fringe of fine, straight hairs; blades involute, at least 5 mm. broad at the base.
Inflorescence of several to many spikes, erect, not crowded, 4-9 cm. long, arranged in a raceme; spikelets 1-flowered, articulate below the glumes, borne in two rows on one side of the rachis, closely crowded; glumes scabrous, the first very narrow, about 6.5 mm. long including the awn tip, the second exceeding the floret, 8-9 mm. long exclusive of the stout awn 2-4 mm. long; lemma keeled, 1-nerved, about 8 mm. long, shorter than the delicate, 2-nerved palea.