Common reed (Phragmites australis)

California Pest Rating for

 Common reed (Phragmites australis):
 Phragmites australis cf. subsp. altissimus (non-native)
Pest Rating: C |  Proposed Seed Rating: R
— and —
Phragmites australis subsp. americanus (native)
Pest Rating: D |  Proposed Seed Rating: None


Initiating Event:

Phragmites australis has been given a Q rating by the CDFA botany laboratory.

History & Status:

Background: Common reed is a tall, erect, perennial wetland grass, 1 to 3 meters high. It spreads via rhizomes and seeds. Local spread of Common reed is predominantly through vegetative growth and regeneration, while establishment of new populations occurs through dispersal of seeds, rhizomes, and sod fragments. Common reed is one of the most widely distributed flowering plants. It occurs on every continent except Antarctica and is cosmopolitan in temperate zones. Common reed is widely distributed in North America; it occurs in all U.S. states except Alaska. Common reed is native to Puerto Rico and occurs as a nonnative in Hawaii. That said, populations in different continental areas vary in their morphology, haplotypes, genetics, and ecology. These different forms have been given sub-specific status in some cases. Research has shown that an adventive form (tentatively identified as Phragmites australis subsp. altissimus), probably introduced from the Western Europe in the late 19th century, had colonized wide areas in North America and had largely displaced native ecotypes in the northeastern U.S. by 1940. This form is considerably more invasive than native ecotypes and displays much higher productivity and ability to invade a variety of wet habitats.

Large infestations of Common reed are difficult to eradicate given that all rhizomes must be removed or killed to prevent re-sprouting. In addition care must be taken to ensure that only the invasive, non-native subspecies is removed. Typically a combination of mechanical removal and application of a systemic herbicide (e.g., glyphosate) provide the best control.

Common reed is listed as a noxious weed in Alabama, Connecticut, Massachusetts, South Carolina, Vermont, and Washington. Much of the weed management budget in Nebraska is spent on controlling the non-native ecotype of common reed.

 Worldwide Distribution: Common reed is native to many warm temperate and tropical regions from throughout the world. The non-native subspecies seems to have been introduced from western Europe.

California Distribution: Common reed is found along waterways throughout much of CA. It is rarely collected in the Central Valley of California, but it is extremely common in the Delta Region.

California Interceptions: Common reed is occasionally sold in nurseries in CA. Plumes of unknown sub-specific identity are also used in dried plant arrangements imported from Asia and other areas.

This risk Common reed would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California.

– Low (1) not likely to establish in California; or likely to establish in very limited areas
-Medium (2) may be able to establish in a larger but limited part of California
-High (3) likely to establish a widespread distribution in California

Risk is Medium (2) as illustrated by the broad distribution of the invasive form in other states. It is limited by its preference for wetlands and ditches.

2) Pest Host Range:

Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
High (3) has a wide host range

Risk is High (3) as weeds do not require any one host, but grow wherever ecological conditions are favorable.

3) Pest Dispersal Potential:

Evaluate the dispersal potential of the pest:

-Low (1) does not have high reproductive or dispersal potential
-Medium (2) has either high reproductive or dispersal potential
High (3) has both high reproduction and dispersal potential

Risk is High (3) as the plant spreads via water flow and human dispersal from rhizomes or stem fragments. It expands it range via seed dispersal or rhizome fragments.

4) Economic Impact:

Evaluate the economic impact of the pest to California using these criteria:

A.  The pest could lower crop yield

B.  The pest could lower crop value (includes increasing crop production costs)

C.  The pest could trigger the loss of markets (includes quarantines by other states or countries)

D.  The pest could negatively change normal production cultural practices

-Low (1) causes 0 or 1 of these impacts
Medium (2) causes 2 of these impacts
-High (3) causes 3 or more of these impacts

Risk is Medium (2) as Common reed can invade agricultural land, especially along irrigation canals and in rice paddies. Non-native common reed is much more likely to colonize small water features and channels than native ecotypes. It also forms larger, denser colonies than the native subspecies. In these situations it can block or slow irrigation water and cause water loss via evapotranspiration. It can lower yields in some ranching systems, where Common reed may block livestock access to water.

5) Environmental Impact

Evaluate the environmental impact of the pest on California using the following criteria:

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes

B.  The pest could directly affect threatened or endangered species

C.  The pest could impact threatened or endangered species by disrupting critical habitats

D.  The pest could trigger additional official or private treatment programs

E.  Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

-Low (1) causes none of the above to occur
-Medium (2) causes one of the above to occur
High (3) causes two or more of the above to occur

Risk is High (3) as non-native common reed can be  an ecological transformer; it can exclude native riparian species, and dry out or cover small open water sources. Native ecotypes can be dominant in large wetland situations, but non-native ecotypes are much more likely to invade and cause impacts in smaller, isolated water sources. This may have a significant impact on wildlife in arid California, where access to small or isolated water sources plays an important part in population success of some species.

Consequences of Introduction to California for Common reed: 

Rating (Score): Add up the total score and include it here

-Low = 5-8 points
-Medium = 9-12 points
-High = 13-15 points

Total points based on above criteria, which does not take into account the pathogen’s already wide distribution in California: High (13).

6) Post Entry Distribution and Survey Information:  Common reed is widespread in CA. It receives a Low (-1) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Not established (0) Pest never detected in California, or known only from incursions.
Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

 Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score:
Medium (12)


Unfortunately, there is almost no discrimination between native and non-native ecotypes of common reed in California in past literature and on specimen labels. Recent genetic work has indicated that much of the common reed in California, especiually in the Delta region, is the non-native ecotype.

Conclusion and Rating Justification:

Proposed Rating: based on the score listed above the pest is a moderate risk species. This would justify an “A” rating if the species is not widely established in CA already.

As the non-native ecotype’s current range in California is widespread, a “C” rating is recommended for the non-native subspecies and a “D” rating is recommended for the much less invasive native subspecies.


Amsberry, L., M. A. Baker, P. J. Ewanchuk, & M. D. Bertness. 2000. Clonal integration and the expansion of Phragmites australis. Ecological Applications. 10: 1110-1118.

Plut, K., J. Paul, C. Ciotir, M. Major & J. R. Freeland. 2011. Origin of non-native Phragmites australis in North America, a common wetland invader. Fundam. Appl. Limnol. 179: 121–129.

Invasive Plants. Common reed. Accessed 8/20/2015:

Papchenkov V.G. 2008. About distribution of Phragmites altissimus (Benth.) Nabille (Poaceae). Russian J. of Biological Invasions 1: 202-205.

Randolph M. Chambers R. M., L. A. Meyerson, & K. Saltonstall. 1999. Expansion of Phragmites australis into tidal wetlands of North America.  Aquatic Botany 64: 261–273.

Saltonstall, K. 2002. Cryptic invasion by a non-native genotype of the common reed, Phragmites australis, into North America. Proc Natl Acad Sci USA 99: 2445–2449.

Saltonstall, K.,& J. Stevenson. 2007. The effects of nutrients on seedling growth of native and introduced Phragmites australis. Aquatic Botany. 86: 331-336.

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0312;[@]

Comment Period: CLOSED

The 45-day comment period opened on Tuesday, April 5, 2016 and closed on May 20, 2016.

Phragmites australis cf. subsp. altissimus (non-native)
Pest Rating: C |  Proposed Seed Rating: R
Phragmites australis subsp. americanus (native)
Pest Rating: D |  Proposed Seed Rating:  None

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