Culms: 1-4 m tall, 0.5-1.5 cm thick, erect. Ligules: about 1 mm; blades: 15-40 cm long, 2-4 cm wide, long-acuminate, disarticulating from the sheath at maturity. Panicles: 15-35 cm long, 8-20 cm wide, ovoid to lanceoloid, often purplish when young, straw-colored at maturity. Spikelets: with 3-10 florets; rachilla hairs: (4)6-10 mm. Lower glumes: 3-7 mm; upper glumes: (4)5-10 mm; lemmas: 8-15 mm, glabrous, linear, margins somewhat inrolled, apices long-acuminate; paleas : 3-4 mm, membranous; anthers: 1.5-2 mm, purplish; style: persistent. Caryopses : 2-3 mm, rarely maturing. 2n = 36, 42, 44, 46, 48, 49-54 2n = 36, 42, 44, 46, 48, 49-54 [H.E. Connor, M.I. Dawson, R.D. Keating, and L.S. Gill. 1998. Chromosome numbers of Phragmites australis (Arundineae:Gramineae) in New Zealand. New Zealand J. Bot. 36:465-469], 72, 84, 96, 120 [Y. Ishi and Y. Kadono. 2000. Classification of two Phragmites species, P. australis and P. japonica, in Lake Biwa-the Yodo River system, Japan. Acta Phytotax. Geobot. 51:177-186].

Phragmites australis grows in wet or muddy ground along waterways, in saline or freshwater marshes, and in sloughs throughout North America. Its tall, leafy, often persistent culms and plumose panicles make it one of our easier species to recognize. In Florida, Neyraudia reynaudiana is sometimes mistaken for P. australis, but the former has glabrous internodes and pilose lemmas. There are three distinct strains in North America north of Mexico, one of which is invasive. Two of the strains are treated as subspecies.

Phragmites australis is one of the most widely distributed flowering plants, growing in most temperate and tropical regions of the world, spreading quickly by rhizomes. Once established, it is difficult to eradicate. Its uses include thatching, lattices, arrow shafts, construction boards, mats, and erosion control, and it was used in the past to make cigarettes and superior pen quills.