A large perennial grass found in wetlands throughout temperate and tropical regions of the world. Phragmites are an invasive species in North America. Gallic acid released by Phragmites is degraded by ultraviolet light to produce mesoxalic acid, effectively hitting susceptible plants and seedlings with two harmful toxins. Phragmites are so difficult to control that one of the most effective methods of eradicating the plant is to burn it over 2 to 3 seasons. The roots grow so deep and strong that one burn is not enough.
The erect stems grow to 2 to 6 meters tall. The leaves are long for a grass, 8 to 20 inches and 0.8 to 1.2 inches broad. The flowers are produced in late summer in a dense, dark purple panicle, about 20 to 50 cm long. Later the numerous long, narrow, sharp pointed spikelets appear greyer (brownish) due to the growth of long, silky hairs.