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Montana Field Guide

Montana Field Guides

American Common Reed - Phragmites australis ssp. americanus
Other Names:  Common Reed

Native Species

Global Rank: G5T5
State Rank: S4
(see State Rank Reason below)
C-value: 3

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In Montana, Phragmites australis ssp. americanus is native and scattered across many western, central, and northeastern counties. With a little training this native subspecies can be differentiated from the exotic subspecies, australis. Populations form small, somewhat dense, and almost monotypic stands. On the landscape these small, nearly monotypic populations are intermixed with other plant communities, and appear to expand very slowly.
General Description
PLANTS (species level): Cool season, rhizomatous perennial. Stems 1.5-3.5 m, forming dense stands (Lesica 2012).

LEAVES (species level): Blades 2–4 cm wide, flat and lax to ascending; sheaths with overlapping margins; ligules hairy, 3–6 mm long (Lesica 2012).

INFLORESCENCE (species level): A plumose panicle 15–32 cm long. Spikelets 11–14 mm long, with 3 to 8 florets, the florets covered by silky hairs from the rachilla; glumes shorter than the florets. Lemmas hairless, with an awn-like tip; the rachilla with long silky hairs; palea well developed. Disarticulation above the glumes; unit of dispersal the floret (Lesica 2012).

In Montana, common reed consists of two subspecies (ssp.): ssp. americanus is native and more common while ssp. australis is introduced and very localized. Populations can be easily identified to the subspecies level (see diagnostic characteristics).

Diagnostic Characteristics
The MTNHP is tracking locations of common reed grass at the subspecies level. It is possible that both subspecies can be found adjacent to each other, yet be distinguishable. Consider submitting your observation data to MTNHP.

Phragmites australis subspecies americanus is native [Adapted from Michigan State University Extension (no date)]:
STEM COLOR/LEAF SHEATHS: Sheaths easily fall off, exposing the stem which will turn bright red when exposed to sunlight.
LIGULES: The width of the ligule membrane (not including the fringe of hairs at the top) is the critical measure. The ligule membrane is slightly wider, ranging from 0.4-1.0 mm tall.
GLUMES: In a spikelet, the first (or lowest) glume is relatively longer, ranging from 4-7 mm.
GROWTH FORM: It is less robust, typically reaching 6 feet. It grows a bit more scattered, allowing for light to penetrate through the canopy and for other plants to colonize. Where nutrient availability is high, it will grow denser and taller. Stems break down easily over winter, allowing for other plants to grow.

Phragmites australis subspecies australis is exotic [Adapted from Michigan State University Extension (no date)]:
STEM COLOR/LEAF SHEATHS: Sheaths cling tightly to stem, covering the dull, tan stem. It grows stolons, which are horizontal stems that spread on the soil surface.
LIGULES: The width of the ligule membrane (not including the fringe of hairs at the top) is the critical measure. The ligule membrane is slightly narrower, ranging from 0.1-0.4 mm tall.
GLUMES: In a spikelet, the first (or lowest) glume is relatively shorter, ranging from 2.6-4.2 mm.
GROWTH FORM: It forms dense monocultures, outcompeting native species. Stems can grow to 18 feet. Where nutrient availability is high, it will grow denser and taller. Stems do not break down slowly, maintaining a thick thatch.

Sterile specimens of Phragmites are superficially similar to Arundo, a weedy, non-native species that gets as far north as Malheur County, Oregon (Lesica 2012). The genera can be distinguished based on glumes. The glumes of Phragmites are glabrous and shorter than the lemmas. The glumes of Arundo longer than the florets and covered with soft, whitish hairs 6-8 mm long.

Range Comments
Phragmites australis is found on every continent except Antarctica and may have the widest distribution of any flowering plant (Tucker 1990). It is common in and near freshwater, brackish and alkaline wetlands in the temperate zones world-wide. It may also be found in some tropical wetlands but is absent from the Amazon Basin and central Africa. It is widespread in the United states, typically growing in marshes, swamps, fens, and prairie potholes, usually inhabiting the marsh-upland interface where it may form continuous belts (Roman et al. 1984). In Montana is occurs in a lot of western, central, and northeastern counties.

Observations in Montana Natural Heritage Program Database
Number of Observations: 40

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Margins of ponds, marshes, and river floodplains (Lesica 2012). Often where there is disturbance.

Phragmites australis provides food, cover, and nesting habitat for small mammals, muskrats, waterfowl, rabbits, pheasants, song birds, and other animals. (Gucker 2008). The type and the degree of use by native birds and mammals seems to reflect geography, species, and availablity of resources. It can be good thermal cover for white-tailed deer and mule deer. In Montana it provides forage and thermal cover for many species of birds and small mammals. For pronghorn it is considered a fair food source, and for mule deer, white-trailed deer, and elk it is considered a poor food source in Montana. Common Muskrats use stem for food and for nesting material. Waterfowl eat their seeds while Black-capped chickadees (and other birds) eat the scales (Caetococcus phragmitidis) which commonly live on the leaf sheaths. In Montana this species is used by Red-wing and Yellow-headed Blackbirds. In other regions songbirds, Barn Owls, and Red-winged Hawk may use stands for foraging and/or roosting. Plants may also provide habitat for aquatic species, though, the exotic subspecies can also change the ecology of aquatic systems.

Livestock (cattle and horses) may feed on Phragmites australis before it matures; although, some studies report that is has little to no forage value (Gucker 2008). The amount of use and nutritional value might depend upon geography and what other forage is available.

Economic Value
Native Americans used Phragmites australis subspecies americanus for food, shelter, medicines, tools, and spiritual practices. Please consult the Fire Effects Information System for Phragmites australis (Gucker 2008) webpage for more information and literature on this subject.

Management of Phragmites australis is dependent upon the subspecies. It is important to accurately identify the subspecies before implementing any management action. In Montana, land managers are encouraged to maintain and native common reed populations while eradicating non-native populations. The establishment, spread, and increase in abundance of the non-native Phragmites australis subspecies australis is associated with human-caused disturbances, such as from land development, tidal manipulation, and waterway construction.

The native Phragmites australis subspecies americanus has attributes (rhizomatous and dense growth form) that make can make it desirable in reclamation projects, such as in controlling erosion. Care should be taken to ensure that only the native subspecies is seeded or planted. In Montana, native Phragmites australis subspecies americanus stands appear to be small monocultures that occur in a matrix with other plant communities; however, plants can create enough openings to allow other plants to co-exist.

In portions of the U.S. Phragmites australis been called an "ecosystem engineer" because dense, monotypic stands can change plant richness, soil properties, sedimentation rates, animal habitat use, and food webs (Gucker 2008). Large stands of Phragmites australis have been found to decrease plant diversity due to its growth form and ability to trap sediment and collect common reed leaf litter. In New Jersey, Phragmites australis stands had lower water salinity, depth to water table, and topographic relief than stands dominated by saltmeadow cordgrass and saltgrass in brackish tidal marshes (Gucker 2008). Further these differences were determined to be significant within three years of Phragmites australis establishment. For a synthesis of studies evaluating impacts or ecosystem changes with respect to Phragmites australis and various native plant habitats, please consult the Fire Effects Information System for Phragmites australis (2008) webpage.

In many parts of the U.S. large monocultures of the non-native Phragmites australis subspecies australis has warranted management actions that includes altering hydrology, herbiciding, applying fire, planting competitive vegetation, and other tactics. It is recommended that Phragmites australis management be site-specific, goal-specific, and value-driven (Gucker 2008). Further, it is imperative to understand the biological, chemical, and physical impacts at the particular site in order to determine the management strategy and process.

Large, monocultures of Phragmites australis can be prevented through management actions that encourage competing vegetation and minimize nutrient loads (Gucker 2008). Phragmites australis spreads faster in areas with high-nutrient availability, particularly where competiting vegetation has been removed or reduced. The timing and intensity of hydrological changes can also impact Phragmites australis stands. Please consult the Fire Effects Information System for Phragmites australis (2008) webpage for a synthesis of studies and literature on this subject.

Prescribed fire is not recommended for controlling the Phragmites australis subspecies australis. Plants grow in wet environments which are often poorly affected by fire and where other native plants are not adapted to fire. Phragmites australis subspecies australis plants may be top-killed by fire, but their rhizomes usually survive and will re-sprout(Gucker 2008). Unless rhizomes are killed, fire can stimulate re-sprouting (Gucker 2008). In the short-term, fire may decrease plants, but if viable rhizomes remain than stands will re-colonize (Gucker 2008).

  • Additional ReferencesLegend:   View Online Publication
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    • Gucker, Corey L. 2008. Fire Effects Information System (FEIS) for Phragmites australis. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).
    • Hale, K.M. 2007. Investigations of the West Nile virus transmission cycle at Medicine Lake National Wildlife Refuge, Montana, 2005-2006. M.Sc. Thesis. Bozeman, MT: Montana State University. 74 p.
    • Michigan State University Extension. No Date. Phragmites australis identification pamphlet
    • Sater, S. 2022. The insects of Sevenmile Creek, a pictorial guide to their diversity and ecology. Undergraduate Thesis. Helena, MT: Carroll College. 242 p.
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Citation for data on this website:
American Common Reed — Phragmites australis ssp. americanus.  Montana Field Guide.  .  Retrieved on , from