Calamagrostis cinnoides is a perennial grass, 60 cm to 1.2 m tall, stems stout, smooth, solitary or few together, colonial from rhizomes.
Leaves alternate, blades 5-30 cm long, 0.5-1 cm wide, smooth to rough textured.
Flower spikelets to 0.7 cm long, 1-flowered, first glume 0.5-0.8 cm, second slightly shorter, tips pointed, curved outward, longer than lemma; lemma 0.4-0.6 cm, hairy at base, hairs half as long as lemma, awn arising from above middle of back, straight, barely longer than lemma; inflorescence 10-20 cm long, 2-5 cm wide, branched but appearing spike-like, erect, dense, branches strongly ascending, rough textured; blooms and fruits July-Oct.
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Open marshes or swamp forests, moist sandy or peaty soil pH 4-7; intolerant to shade, fire, salt, drought (USDA, NRCS 2010).