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Phragmites Identification Page
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Article Content
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Common Reed (Phragmites australis)
Oregon "A" Designated Noxious Weed
Phragmites australis is a large, perennial grass with creeping rhizomes and stolons,
and terminal, plume-like flowering stalks. Common reed has woody hollow stems that can grow to 1-4 meters tall with stem diameters of 0.5-1.5 cm. Leaves are 15-40 cm long with an open leaf sheath. 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 (Saltonstall 2003, Saltonstall et al. 2004). Accurately distinguishing these from one another is important for the purposes of habitat conservation and/or restoration as well as reducing the impact and spread of invasive species.
Distinguishing native from non-native stands
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 yellow-brown 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.
Information on Oregon Phragmites populations (native and introduced) is important. Submit Phragmites plant samples for determination or provide location information to Vanessa Howard Morgan Center for Lakes and Reservoirs, PSU vhoward@pdx.edu, phone: 503-725-2937.
Additional Information Links and Materials
ODA Common Reed (phragmites) Profile
WeedMapper Profile and Maps
Phragmites ID Pamplet (printable)
Characteristics to differentiate introduced and native Phragmites
If the population has at least two characteristics from Group A
and three from Group B, the population is most likely introduced.
GROUP A
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Introduced
Phragmites australis ssp. australis
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Native
Phragmites australis ssp. americanus
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Leaf Sheaths
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Tightly clasping, hard to pull off, abundant
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Easily pulled off, sparse, loosely attached |
Stem Denisty
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Monotypic, dense, excludes other plant species
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Not monotypic, other plant species incorporated |
Ligule Width
(ligule: membranous outgrowth where leaf sheath meets culm or stem)
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Narrow: 0.4-0.9mm
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Wide: 1.0-1.7mm
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Glume Length
(glume: the outermost and lowest bracts of a floret)
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Introduced:
Shorter: Upper Glume 4.5-7.5mm
Lower Glume: 2.5-5.0mm
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Native:
Longer: Upper Glume 5.5-11.0mm
Lower Glume: 3.0-6.5mm
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Group B
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Introduced
Phragmites australis ssp. australis
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Native
Phragmites australis ssp. americanus
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Stem Height
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3-6 meters |
1-4 meters
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Stem Texture
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Raised ridges running vertically on stem |
Smooth, no ridges |
Stem-Spots
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Typically no spots present |
Small, round, dark fungal spots may be present |
Rhizome Size & Shape
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Squashed or compressed (oval), >15mm in diameter |
Round, <15mm in diameter |
Stem Color At Base
(during growing season)
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Typically all green
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Typically green with maroon or brown |
Leaf Color
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Blue-green
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Yellow-green, lighter than introduced
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Inflorescense Size
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Typically larger than native |
Typically smaller than introduced |
Colonal Expansion Rate
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Very rapid
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Slow and steady |
Characteristics described here were compiled from: Saltonstall, K. Plant Conservation Alliance's Alien Plant Working Group Least Wanted Fact Sheet:
Common Reed -Phragmites australis http://www.nps.gov/plants/ALIEN/fact/phau1.htm
Ecology and Management of Invasive Plants -Morphological differences between native and introduced genotypes http://invasiveplants.net/phragmites/morphology.htm
Photos reproduced with permission from Vanessa Howard Morgan, Kirstin Saltonsall, Richard Meadows, and Tim Butler.
Special thanks to Vanessa Howard Morgan and Lynda K. Moore for the deveolopement of the Phragmites Field Guide and for allowing the use of it in the development of this web page.
Vanessa Howard Morgan
Center for Lakes & Reservoirs
Portland State University
503.725.2937 phone
503.725.3834 fax
www.clr.pdx.edu
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