Distribution: British Columbia to Baja, California, east to Newfoundland and Florida.
Habitat: Wet meadows to shallow marshes, mostly emersed.
Flowers: May - October
Conservation Status: Not of concern
Dioecious, aquatic perennials from rhizomes, the stems erect, 6-12 dm. tall.
Leaves flat, slightly keeled beneath, 3-8 dm. long and 8-15 mm. broad.
Flowers in globose clusters toward the tip of the main stem; inflorescence branched, 1.5-4 dm. long, the branches with 5-12 staminate heads and 1-2 pistillate heads, the latter 20-26 mm. thick when mature; stamens 3-5 with 3-5 minute, chaffy bracts; pistil 1, the style 2-cleft; stigmas 2, linear, 2 mm. long.
Fruit a nutlet-like achene, 2-seeded, rounded, up to 10 mm. long, narrowed very abruptly to the stylar beak.