Zannichellia palustris is a submersed monocotyledon, rooted aquatic herb, colonial from rhizomes, rooting at nodes, tendril-like coiled adventitious roots may help anchor plants (Sculthorpe 1985).
Leaves opposite or apparently in whorls of 3-4, linear, filament-like, to 10 cm x 0.5 mm, 1-veined.
Flowers axillary, very small, no petals or sepals.
Fruit an achene to 0.3 cm, plus beak of 0.1 cm, body slightly asymmetric and keeled around margin (like a tiny, short green bean), often in pairs or whorls or 3-4 in axils; blooms and fruits July-Oct.
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Fresh, often high nutrient, or brackish water.
Notes: Seeds and plants eaten by many species of duck (Martin et al. 1951). Widespread in N. America but fossils found in Britain and Western Europe (Sculthorpe 1985).