Common reed (Phragmites australis)

Common reed (Phragmites australis)
Images courtesy Glenn Miller
Common reed (Phragmites australis)
Common reed (Phragmites australis)
EDRR Species?: 
No

Other common names
Giant reed, Phragmites, Giant reedgrass, Roseau cane, Yellow cane

Description
A large, perennial, clonal grass species with creeping rhizomes and stolons and terminal, plume-like flowering stalks. This plant has woody, hollow stems that can grow 1 to 4 meters tall with stem diameters of 0.5 to 1.5 cm. Leaves are 15 to 40 cm long with an open leaf sheath. Common reed 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 11 cm per day; they 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). 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 river systems, this tends to be the dominant means of expansion and dispersal. There is no evidence of hybridization between native and introduced lineages. Recent genetic studies indicate there are various lineages of common reed present in the United States; one of these is native to North America, including the Pacific Northwest, while another is introduced and has recently begun to spread. Differences between the two subspecies can be subtle and may partially depend on ecological conditions. The native has a reddish-purple lower internode color as opposed to yellow-brown for the non-native species. Native plants have longer lower glumes, as well as longer ligules (on middle leaves), compared to non-native plants.

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