The following narrative s excerpted from http://www.invasiveplants.net/phragmites/Default.htm
Phragmites australis, or common reed, is a wetland plant species found in every U.S. state.
It can grow up to 6 meters high in dense stands and is long-lived. Phragmites is capable of reproduction by seeds, but primarily does so asexually by means of rhizomes. Recent research has now shown that native and introduced genotypes of this species currently exist in North America.
Phragmites australis (Fig. 1), is widely distributed, ranging all over Europe,
Asia, Africa, America and Australia, however, the origin of the species is unclear.
Until recently the status of the plant as native to North America or introduced has been in dispute but new work has demonstrated the existence of native and introduced genotypes of P. australis
Phragmites australis is a clonal grass species with woody hollow culms which can grow up to six meters in height. Leaves are lanceolate, often 20-40 cm long and 1-4 cm wide. Flowers develop by mid summer and are arranged in tawny spikelets with many tufts of silky hair. P. australis is wind-pollinated but self-incompatible. Seed set is highly variable and occurs through fall and winter and may be important in colonization of new areas. Germination occurs in spring on exposed moist soils. Vegetative spread by below-ground rhizomes can result in dense clones with up to 200 stems/m2.
Distribution and Spread:
P. australis is most abundant along the Atlantic Coast and in freshwater and brackish tidal wetlands of the northeastern United States as far south as North Carolina. It occurs in all eastern states and populations are expanding, particularly in the Midwest. At present, P. australis occurs throughout the entire United States (except Alaska and Hawaii) and southern Canada.
The following line drawings are from this link: http://plants.usda.gov/cgi_bin/topics.cgi?earl=plant_profile.cgi&symbol=PHAU7 – additional information is available there on Phragmites