Cyperus pseudovegetus is a perennial sedge growing in tufts; rhizomes upright, 0.5–0.8 cm wide, hard; stems 3-sided, 30-50 (80) cm tall, ca. 0.2 cm wide (Flora of North america www.efloras.com).
Leaves elongate, often longer than flowering stem, 0.4-0.6 cm wide, folded along midrib. Inflorescence bracts 4-8, 40–60 cm long, 0.5–0.8 cm much longer than flowering stem.
Flower spikes half round (hemispheric), 0.7–1.5 cm wide, very dense, rays (stems of the spikes) 3–6, 0.1–3.0 cm each with a dense cluster (glomerule) of ; inflorescence bracts 10–15, V-shaped in cross section, 6–30 cm long 0.5–0.8 cm wide; Spikelets 40–100, greenish white, flattened, egg-shaped in outline, 0.4-0.5 cm long, 0.3–0.4 cm wide; flower scales oblong, widest above the middle, light greenish to light brown, ca 0.2 cm long, 0.1 cm wide, 3-ribbed, with 2 longitudinal ridges (keels) at the base (use lens), curved inward, the tip bent outward with a small, sharp point (mucronate).
Fruit a dry achene, styles of the flower thick, persistent on the achene; achene brown, linear, slightly curved, 3-sided, ca 0.1 cm long, base whitish, surface minutely warty (papillose),tip pointed; borne on a spongy stalk (stipe) ca 0.01 ca long (Flora of North America www.eFloras.com 2016; Vol. 23 Page 143).
Wetland status: FACW
Frequency in NYC: Very infrequent.
Habitat: Swamps, marshes.
Notes: A southern plant. Formerly found north only to southern NJ. Listed as endangered in NJ.