Sparganium eurycarpum is an emergent aquatic perennial monocotyledon herb, to 1.8 m tall; colonial from rhizomes rooted in mud.
Leaves to 80 cm long 2 cm wide, cat-tail-like but more yellow green, midrib prominent, stiff, keeled in back.
Flowers very similar to S. americanum, green, female flowers with 2 stigmas, in stalkless, ball-shaped, spiky clusters, male flowers in smaller clusters above females along inflorescence stems about 2-3 cm wide, at base of zigzag stem above a leaf-like bract.
Fruit dry achenes, reverse-pyramidal-shaped (obconical), widest at top, hard.
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Edges of open ponds in shallow water.