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Phragmites Identification Page
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.




Phragmites australis ssp. australis


Phragmites australis ssp. americanus

Leaf Sheaths

Common Reed Sheath
Native Reed Sheaths
Tightly clasping, hard to pull off, abundant 
Easily pulled off, sparse, loosely attached  

Stem Denisty

 Introduced stand Native stand
  Monotypic, dense, excludes other plant species
Not monotypic, other plant species incorporated

Ligule Width

(ligule: membranous outgrowth where leaf sheath meets culm or stem)
 Introduced ligule Native ligule
  Narrow: 0.4-0.9mm
Wide: 1.0-1.7mm

Glume Length

(glume: the outermost and lowest bracts of a floret) 
Phragmites Introduced glume length
Phragmites Native glume length

Shorter: Upper Glume 4.5-7.5mm
Lower Glume: 2.5-5.0mm

Longer: Upper Glume 5.5-11.0mm
Lower Glume: 3.0-6.5mm



 Group B



Phragmites australis ssp. australis


Phragmites australis ssp. americanus

Stem Height

3-6 meters  1-4 meters

Stem Texture

Raised ridges running vertically on stem Smooth, no ridges


Typically no spots present   Small, round, dark fungal spots may be present

Rhizome Size & Shape

Squashed or compressed (oval), >15mm in diameter  Round, <15mm in diameter

Stem Color At Base

(during growing season)
Typically all green
Typically green with maroon or brown

Leaf Color

Phragmites Leaf Blades
Phragmites Leaf Blades
Yellow-green, lighter than introduced

Inflorescense Size

Typically larger than native Typically smaller than introduced

Colonal Expansion Rate

Very rapid
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