Species Information

• common reed (giant reed, phragmites, giant reedgrass, yellow cane)
• Phragmites australis
• USDA Symbol: PHAU7
• Oregon Noxious Weed Designation: A
• Pictures

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Identification:

Phragmites australis is a large, perennial, clonal grass species with creeping rhizomes and stolons, and terminal, plume-like flowering stalks. Known as common reed this plant has woody hollow stems that can grow 1-4 meters tall with stem diameters of 0.5-1.5 cm. Leaves are 15-40 cm long with an open leaf sheath. Phragmites grows in a wide range of sites that hold shallow water, including roadside ditches, marshes, swamps, brackish estuaries, and alkaline wetlands. Reproduction is primarily vegetative, through an extensive network of rhizomes, which can grow horizontally up to 1.8 m per year depending on the climate. Stolons are produced in young stands or over open water, growing up to 11cm per day, and further aid in rapid stand expansion and dispersal during storm events. This plant will inhabit any slight depression that has an ability to hold water. It has become increasingly common along railroad tracks, roadsides, and dredge spoils. Seeds are shed from November through January and are dispersed by wind, water, and animals. Once seeds germinate and become established, young plants usually persist for at least two years in a small, inconspicuous stage where they resemble many other grass species. When seedlings establish in inland or low salinity areas, the infestation will typically expand radially, resulting in distinct circular patches. In higher salinity areas, infestations established at the water’s edge expand inward toward the center of the marsh. Plants tend to grow taller and exhibit fewer dead leaves the further from shore they grow (down the salinity gradient) (Adams and Bate, 1999). Long distance seed dispersal is accomplished by water, wind, and wildlife. Asexual reproduction occurs during flood events and tidal exchanges, which undercut root masses dispersing the root fragments downstream and onto flood plains. In rivers systems, this tends to be the dominant means of expansion and dispersal. There is no evidence of hybridization between native and introduced lineages (Saltonstall et al. 2004). Recent genetic studies indicate there are various lineages of common reed present in the United States; one of these is native to the Pacific Northwest while another is introduced and has recently begun to spread (Saltonstall 2003, Saltonstall et al. 2004). Differences between the two subspecies can be subtle and may partially depend on ecological conditions. Morphological work has focused on ligule’s length, lower glume length and stem characteristics such as sheath persistence and internode color. The native has a reddish-purple lower internode color as opposed to yellowbrown for the non-native P. australis subsp. australis. Native plants have longer lower glumes as well as longer ligules (on middle leaves) compared to non-native plants.

Impacts:

Non-native Phragmites is frequently regarded as an aggressive, unwanted invader. Studies have shown Phragmites dominated areas exclude large wading birds; exhibit decreased overall species richness of birds (Chambers et al. 1999) and reduces feeding grounds for birds through increased bank steepness (Teal and Peterson 2005). Phragmites increases land elevation, reducing habitat for important fish species and disrupts trophic transfers within the marsh itself as well as the greater estuary. Both small and large fish suffer from low biomass and decreased body lengths as a result of Phragmites infestations (Hagan et al. 2007). Phragmites can block fish passage by bridging marsh creeks and reduce refuge by steepening creek banks (Teal and Peterson 2005). Native decomposition rates are slowed because of the high concentration of lignin in Phragmites stems yet the fast rates of leaf decomposition can alter soil invertebrate communities. Marsh specialists are often replaced with generalists in Phragmites dominated areas (Chambers et al. 1999) and native plant diversity is dramatically reduced. In addition, Phragmites can have adverse impacts on waterfront property values and recreation such as hunting and fishing. Disturbances or stresses such as pollution, dredging, and increased sedimentation favor invasion, and spread of non-native Phragmites.

Biological Controls:

Biological control agents are not used on "A" listed weeds in Oregon. This weed is being managed for eradication or containment.

Oregon Maps of Common Reed Distribution

Links:

Oregon Department of Agriculture information on common reed

USDA Plants Database information on common reed

GRIN Database information on common reed