American reedgrass (common reed)
Poaceae (Grass family)
Introduction to Vascular Plants
Map
Distribution of Phragmites australis subsp. americanus
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Introduction
The genus Phragmites is one of the most widely distributed genera in the world (Allred 2010) and is found across most of North America, excluding the Yukon, Alaska, Labrador, and Nunavut (USDA 2010). This is an easily recognized genus of tall (to 3 m), rhizomatous or stoloniferous grasses that form dense stands in saline or freshwater wetlands, including cattail marshes, sloughs, ponds and ditches. The taxonomy of the genus is not yet clear. However, in BC, two subspecies are now recognized. These are:
1) the introduced Phragmites australis subsp. australis (European common reed), an aggressive, invasive subspecies of European origin that is present along the Atlantic coast (where it is invading saltmarshes) and in several locations in British Columbia (Snyder 2009, Martin 2003, Lomer pers. comm. 2011, Brown pers. comm. 2011, Marr pers. comm. 2011). These include Vernon, Osoyoos, Richmond, Burnaby, Galiano Island and Metchosin. 2) the native Phragmites australis subsp. americanus, native to fens, bogs and river shores within its North American range (Catling 2005) and more widespread in BC. The two subspecies are separated on the basis of glume length, culm/stem colour, leaf colour, and habitat. Identification is based on a collection of characters. See the identification section below for more details. Populations of the native subspecies in eastern North America are reported as declining, while populations of the introduced subspecies are spreading throughout North America--this is a successful estuarine invader (Myerson 2009). Research on Phragmites shows that "the native type is a low-nutrient specialist, with a more efficient photosynthetic mechanisms and lower N demand, whereas the introduced type requires nearly four times more nitrogen than the native type to be an effective competitor" (Mozdzer and Zieman 2010). This suggests that anthropogenic modification of wetlands has provided the conditions necessary for success of the introduced type in some regions. Hybridization between the two subspecies is not widely reported but has been demonstrated through hand-pollination by Myerson et al. (2009). |
Species Information
General:
Perennial, tufted grass from fibrous roots, semi-rhizomatous; stems stout, erect, 200-300 cm tall.
Leaves:
Sheaths smooth, loose, twisting in the wind and aligning the blades on one side; blades flat, mostly 20-40 cm long, 10-40 mm wide, usually breaking from the stems by winter; ligules half membrane and half hairs, the innovations mostly membranous, the fringe of hairs late in developing, 1.5-3 mm long.
Flowers:
Inflorescence a large feathery panicle, 15-35 cm long, often purplish, but later straw-coloured; spikelets generally 3- to 6-flowered, 10-15 mm long; lower glumes 4-6 mm long, the upper ones about 6-9 mm long; lower lemmas hairy, unawned, 9-12 mm long, the upper ones generally smaller but with awns often as long as the bodies, smooth, but exceeded by the silky hairs of the rachillas; paleas scarcely half as long as the lemmas; lodicules scarcely 1 mm long; anthers about 2 mm long.
Habitat and Range
Marshes, ponds, lakeshores and ditches in the lowland, steppe and montane zones; infrequent in S and NE BC; circumpolar, N to SW NT, E to NF and NS and S to IN, LA, TX and MX; Eurasia, Trinidad, C America.Taxonomic Keys
The following publication provides field characters and a key for separating subspecies of North American Phragmites:
Swearingen, J. and K. Saltonstall. 2010. Phragmites Field Guide: Distinguishing Native and Exotic Forms of Common Reed (Phragmites australis) in the United States. Plant Conservation Alliance, Weeds Gone Wild. Available Online. Additional sources provide tips for separating the subspecies, most of which use the same traits: glume length, culm/stem colour, leaf colour, habit. These include: Catling (2007), Martin (2003), Blossey (2002) Read the Plant Conservation Alliance page for further information on how to separate the native and introduced types. Read the Invasive Plant Network page on how to separate the two subspecies. |
References
Blossey, B. 2002. Replacement of native North American Phragmites australis by introduced invasive genotypes.BEN - Botanical Electronic News 284
Catling, P. M. 2005. New "top of the list" invasive plants of natural habitats in Canada. BEN - Botanical Electronic News 345.
Catling, P. M. 2007. Canadian Phragmites database – notes for use. BEN - Botanical Electronic News 370
Martin, M. 2003. Common Reed (Phragmites australis) in the Okanagan Valley, British Columbia, Canada. BEN - Botanical Electronic News 318
Myerson, Laura A., David V. Viola and Rebecca N. Brown. 2009. Hybridization of invasive Phragmites australis with a native subspecies in North America. Biological Invasions 12 (1): 103-111.
Mozdzer, Thomas J. and Joseph C. Zieman. 2010. Ecophysiological differences between genetic lineages facilitate the invasion of non-native Phragmites australis in North American Atlantic coast wetlands. Journal of Ecology 98 (2): 451 - 458.
Snyder, Eric. 2009. Invasive common reed (Phragmites australis (Cav.) Trin. ex Steud subsp. australis): first record for Manitoba and the Canadian prairies. Botanical Electronic News #418, December 3, 2009.
USDA. 2010. Plant profile for Phragmites australis. United States Department of Agriculture. Available Online.