Poa palustris is a perennial, 50 cm to 1.5 m tall, tufted from fibrous roots, stem bases purplish.
Leaves with sheaths fairly loose, ligule 0.3-0.5 cm long, membranous; blades 0.1-0.2 cm wide.
Flower spikelets 2-4 flowered, first glume about 0.2 cm, second 0.2-0.3 cm, lemmas webbed at base, 3-5 veins; inflorescence 10-30 cm long, slightly nodding, green to purplish, rather open, branches about 5 per node with numerous spikelets beginning at the middle; June-Aug.
Wetland status: FACW.
Frequency in NYC: Very infrequent.
Habitat: Along stream banks, wet soil, tolerant of partial shade, open swamp forests, soil pH 4.9-7.5, tolerant of fire, moderately tolerant of shade, intolerant of salt, drought (USDA, NRCS 2010).