Bolboschoenus robustus is a perennial C3 rush (Bryson and Carter 1977) 60 cm to1.5 m tall, colonial from tuber-bearing rhizomes, stems stout, sharply, 3-sided.
Leaves alternate, to 1 cm wide, dark green, longer than the inflorescence, top edge of leaf sheath dark, usually rounded upward with a conspicuously striated or wavy pattern just below the dark upper edge.
Flowers dry, papery, very small, petals and sepals reduced to 6 bristles, each flower covered by a brown, finely hairy scale with elongate, 0.2 cm, curved bristle from the cleft tip; flowers densely arranged, 5-20 on each spike, spikes to 3 cm long, 1.5 cm wide, egg-shaped to cylindrical; inflorescence compact with spikes all stalkless or some in clusters of 1-3 on stalks to 4 cm long; inflorescence subtended by 2-4 leaf-like bracts, elongate, very unequal, the longest to 40 cm; blooming and fruiting July-Oct.
Fruit dry 1-seeded (achene) glossy brown to black, about 0.3 cm long, broadest near truncate top with minute appendage.
Wetland status: OBL.
Frequency in NYC: Infrequent.
Habitat: High salt marsh, or near brackish water.
Notes: Roots eaten by muskrats, seeds eaten by numerous songbirds and water fowl (Martin et al 1951). Tolerant of anaerobic soil, alkali, salt, soil pH 6.4-8.4, moderately tolerant of fire, intolerant of shade (USDA, NRCS 2010).