Introduction:
Common reed (Phragmites australis)
Phragmites australis grows on level ground in tidal and non-tidal marshes, lakes, swales and backwater areas of rivers and streams. It is found on sites that are seasonally flooded with not more than 50cm of water. It grows on most soil textures from fine clay to sandy loams and is somewhat tolerant of saline or alkaline conditions. Phragmites australis is especially common along railroad tracks, roadside ditches and piles of dredge spoil, wherever slight depressions will hold water. Throughout most of its range, it typically forms closed mono-dominant stands in both disturbed and pristine areas. It is capable of vigorous vegetative reproduction and its seeds, which are normally dispersed by wind, may be transported by birds that nest among the reeds. The seeds are also dispersed by water. Newly opened sites may be colonised by seed or by rhizome fragments carried to the area in soils and on machinery or naturally in floodwaters. Invasion and continued spread is aided by disturbances or stresses such as pollution, alteration of the natural hydrologic regime, dredging and increased sedimentation. In coastal marshes, spread of Phragmites australis is also facilitated by natural disturbance caused by tidal movements of dead vegetation.
Description:
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; (2) mostly between 10-30cm, but up to 100cm and (3) mostly between 20-100cm, but up to 200cm.
Occurs in:
Coastland, estuarine habitats, lakes, riparian zones, ruderal/disturbed, urban areas, water courses, wetlands.
Habitat description:
Common reed (Phragmites australis) Distribution in North America shown in green.
P. australis is especially common in alkaline and brackish (slightly saline) environments and can also thrive in highly acidic wetlands. 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. 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. It grows on most soil textures from fine clays to sandy loams and is somewhat tolerant of saline or alkaline conditions. 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.
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. For example, restriction of the tidal inundation of a marsh and sedimentation may favour P. australis. 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.
General impacts:
Many populations of Phragmites are “benign” and pose little or no threat to other species and should be left intact. Stable populations may be difficult to distinguish from invasive populations. Phragmites is a problem when and where stands appear to be spreading while other species typical of the community are diminishing. Many Atlantic
Close up of the Common reed (Phragmites australis) Weed.
coast wetland systems have been invaded by it as a result of tidal restrictions imposed by roads, water impoundments, dikes and tide gates. The invasions may threaten wildlife because Phragmites alters the structure and function (wildlife support) of relatively diverse Spartina marshes. In the United States this is a problem on many of the eastern coastal National Fish and Wildlife Refuges. The invasions also increase the potential for marsh fires during the winter when the above ground portions of the plant die and dry out. Dense congregations of redwing blackbirds (Agelaius phoeniceus), which nest in P. australis stands preferentially, increase chances of airplane accidents nearby. The monitoring and control of mosquito breeding is nearly impossible in dense stands. In addition, the invasions can also have adverse aesthetic impacts.
Roots grow down to a depth of about 1 m. 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.
Geographical range:
P. australis is found on every continent except Antarctica and may have the widest distribution of any flowering plant.It is common in and near freshwater, brackish and alkaline wetlands in the temperate zones worldwide. It may also be found in some tropical wetlands but is absent from the Amazon Basin. It is widespread in the United States. Phragmites is present in the Pacific and Gulf states but is not regarded as a problem in most of these areas. In Europe, Phragmites is common and encouraged to grow in many places but has been declining in many areas, particularly in eastern Europe.
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