Uchytil (1992) states that P. australis is a tall, warm-season, perennial, sod-forming grass. The culms are erect, rigid, smooth, and hollow. They may be nearly 2.5cm in diameter and from 2 to 4m tall, terminating in a dense, 30-cm panicle. Leaves arise from the culm and are mostly 25-50cm long and 1-5cm wide. It has an extensive rhizome network and occasionally produces stolons as well. Rhizome depth has been variously reported: (1) 40-100cm (Haslam 1972, in Uchytil, 1992); (2) mostly between 10-30cm, but up to 100cm (Fiala 1976, in Uchytil, 1992); and (3) mostly between 20-100cm, but up to 200cm (Cross and Fleming 1989, in Uchytil, 1992). Roots grow down to a depth of about 1 m. OPBWG (Undated) states that the feathery, plume-like flower head is 13-40cm long and composed of many long branches that point upwards. Narrow clusters of flowers are arranged densely along the branches. The flowers are surrounded by silky white hairs that are purplish at first, becoming tawny to dark brown at maturity. Seeds are brown, thin and delicate. A long, narrow bristle is attached to each seed. The seed and bristle together measure approximately 8mm long.
There is now evidence that although the species itself is indigenous to North America, new, more invasive genotype(s) have been introduced from the Old World (Saltonstall 2002, 2003a). Native genotypes persist across the continent, however the Atlantic coast has been largely taken over by the introduced variety with relict native populations found in only a few sites. Native genotypes are found throughout the Midwest, particularly in natural areas, but introduced populations are also common along roadsides and along the shores of the Great Lakes. West of the Rockies, native populations persist at many sites but introduced ones are found in urban areas . Another variety is found in southern North America from Florida across to the Gulf of California which cannot be described as native or non-native to the Continent due to its presence in Asia and South America. Introduced P. australis can also be found in the Mississippi River Delta (Saltonstall 2003b).
Marks et al. (1993) report that P. australis' rhizomes live for 3 to 6 years and buds develop at the base of the vertical type late in the summer each year. These buds mature and typically grow about 1 metre (up to 10m in newly colonised, nutrient-rich areas) horizontally before terminating in an upward apex and going dormant until spring. The apex then grows upward into a vertical rhizome, which in turn produces buds that will form more vertical rhizomes. Vertical rhizomes also produce horizontal rhizome buds, completing the vegetative cycle. The aerial shoots arise from the rhizomes. They are most vigorous at the periphery of a stand where they arise from horizontal rhizomes, as opposed to old verticals (Haslam 1972, in Marks et al. 1993). Temperature, salinity and water levels affect seed germination. Water depths of more than 5cm and salinities above 20 ppt (2%) prevent germination (Kim et al. 1985, Tucker 1990, in Marks et al. 1993). Marks et al. (1993) state that the germination is not affected by salinities below 10 ppt (1%) but declines at higher salinities. Percentage germination increases with increasing temperature from 16 to 25 deg-C while the time required to germinate decreases from 25 to 10 days over the same temperature range.
Uchytil (1992) states that P. australis has been cultivated and used for many purposes around the world. In Europe, it is used as thatching, to make mats, and as fodder and bedding for cattle. The aerial stems are sometimes used as a cellulose source in the paper and textile industries. Native people of the American Southwest used the stems to make arrow shafts, prayer sticks, weaving rods, pipestems, mats, screens, nets, and thatching. They also used the rootstocks and seeds as food. In the Southwest, it is also used for lattices and in the construction of adobe huts. It is used in many wetland rehabilitation and stabilization projects. It is used to revegetate disturbed riparian areas, control shore erosion, stabilize river and canal banks, and reduce wave action on watershed structures.
P. australis is especially common in alkaline and brackish (slightly saline) environments (Haslam 1972, 1971b, in Marks et al., 1993) and can also thrive in highly acidic wetlands (Rawinski, pers. comm. 1985, in Marks et al. 1993). However, it does not require, nor even prefer these habitats to freshwater areas. It is often found in association with other wetland plants including species from the following genera: Spartina, Carex, Nymphaea, Typha, Glyceria, Juncus, Myrica, Triglochin, Calamagrostis, Galium, and Phalaris (Howard et al. 1978, in Marks et al. 1993). Salinity and depth to the water table are among the factors that control its distribution and performance. Maximum salinity tolerances vary from population to population; reported maxima range from 12 ppt (1.2%) in Britain to 29 ppt in New York state to 40 ppt on the Red Sea coast (Hocking et al. 1983, in Marks et al. 1993). It grows on most soil textures from fine clays to sandy loams and is somewhat tolerant of saline or alkaline conditions (Uchytil, 1992). It occurs in disturbed areas as well as pristine sites. It is especially common along railroad tracks, roadside ditches, piles of dredge spoil, and wherever even slight depressions hold water (Ricciuti 1983, in Marks et al. 1993).
Uchytil (1992) states that it grows on level ground in freshwater marshes, oxbow lakes, swales, and backwater areas of river and streams. Various types of human manipulation and/or disturbance are thought to promote P. australis (Roman et al. 1984, in Marks et al. 1993). For example, restriction of the tidal inundation of a marsh and sedimentation may favour P. australis (Klockner, pers. comm. 1985, in Marks et al. 1993). In some areas, P. australis may have been promoted by the increases in soil salinity that result when de-icing salt washes off roads and into nearby ditches and wetlands (McNabb and Batterson 1991, in Marks et al. 1993).
Marks et al. (1993) state that P. australis is capable of vigorous vegetative reproduction and often forms dense, virtually monospecific stands. Newly opened sites may be colonized by seed or by rhizome fragments carried to the area by humans in soils and on machinery during construction or naturally in floodwaters. Once a new stand of P. australis takes hold, it spreads predominantly through vegetative reproduction. Uchytil (1992) states that annual rhizome lateral spread averaged 40cm in common reed stands in Wisconsin. In Europe, lateral rhizome spread has been as great as 1-2m per year. Stolons, which may grow up to 10.8cm per day, are produced in young stands or over open water and further aid in rapid stand expansion. The plants may produce great quantities of seed. However, in some cases, most or all of the seed produced is not viable (Tucker 1990, in Marks et al. 1993).
Marks et al. (1993) suggest that increases in nutrient concentrations, especially nitrates, are primarily responsible for increases in Phragmites populations. Ironically, eutrophication and increases in nitrate levels are sometimes blamed for the decline of P. australis populations in Europe (Den Hartog et al. 1989, in Marks et al. 1993).
Uchytil (1992) states that P. australis has been used in many wetland rehabilitation and stabilization projects. It is used to revegetate disturbed riparian areas, control shore erosion, stabilize river and canal banks, and reduce wave action on watershed structures.
Principal source: Element Stewardship Abstract for Phragmites australis (Marks et al., 1993)
SPECIES: Phragmites australis (Uchytil, 1992)
Compiler: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Review: Kristin Saltonstall, Horn Point Laboratory, University of Maryland Center for Environmental Science US
Publication date: 2006-03-31
Recommended citation: Global Invasive Species Database (2020) Species profile: Phragmites australis. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=301 on 31-10-2020.