Sparganium americanum is an emergent aquatic, perennial monocotyledon herb, stout, 30 cm to 1 m tall.
Leaves to 1 m long, 0.4-1.2 cm wide, thin, flat, thin, soft, translucent, ascending to floating, midrib occasionally with weak keel.
Flowers green, pistillate (female) flowers with 1 stigma, in stalkless, ball-shaped, spiky inflorescence, 2 cm wide, at base of zigzag stem; male (staminate) heads smaller, above pistillate heads; inflorescence with upper staminate heads above pistillate heads along elongate stalk and with leaf-like bracts below each flowering stem, bracts often dilated at base.
Fruit dry, hard, seed-like (achenes) dull, gray-brown, pointed at both ends, widest near middle 0.3-0.5 cm long. Seeds eaten by water fowl, stems eaten by muskrats (Martin et al. 1951).
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Open mud or shallow water.