Glyceria maxima - (Hartman) Holmb.
Reed Mannagrass
Other English Common Names: English Watergrass, Reed Meadowgrass, Reed Sweetgrass, Tall Glyceria
Taxonomic Status: Accepted
Related ITIS Name(s): Glyceria maxima (Hartm.) Holmb. (TSN 40846)
Unique Identifier: ELEMENT_GLOBAL.2.141191
Element Code: PMPOA2Y0L0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Grass Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Monocotyledoneae Cyperales Poaceae Glyceria
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Glyceria maxima
Conservation Status
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NatureServe Status

Global Status: GNR
Global Status Last Changed: 22Mar1994
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (12Oct2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Massachusetts (SNR), Washington (SNA), Wisconsin (SNA)
Canada British Columbia (SNA), Newfoundland Island (SNA), Nova Scotia (SNA), Ontario (SNA), Quebec (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Other NatureServe Conservation Status Information

Distribution
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U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States MA, WAexotic, WIexotic
Canada BCexotic, NFexotic, NSexotic, ONexotic, QCexotic

Range Map
No map available.

Ecology & Life History Not yet assessed
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Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank)
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Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: High/Low
Rounded I-Rank: Unknown
I-Rank Reasons Summary: Glyceria maxima has the biological attributes and past history in countries with similar habitats to give it extremely high potential as a wetland invader in the U.S. that would be extremely difficult to control. However, it has only been detected in a few locations in the U.S. where it was quickly removed successfully. This species is one which should raise a high alert whenever it is detected in natural areas. Rapid action seems to be a major factor in preventing the spread of G. maxima.
Subrank I - Ecological Impact: High/Medium
Subrank II - Current Distribution/Abundance: Low/Insignificant
Subrank III - Trend in Distribution/Abundance: Medium
Subrank IV - Management Difficulty: High/Medium
I-Rank Review Date: 12Sep2007
Evaluator: Davis, G.
Native anywhere in the U.S?
Native Range: Glyceria maxima is a native in Europe and temperate Asia (Weber 2003).

Download "An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for their Impact on Biodiversity". (PDF, 1.03MB)
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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: Glyceria maxima is established outside of cultivation in Wisconsin (University of Wisconsin 2007) and Massachusetts (USDA PLANTS 2007).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: Glyceria maxima invaded the Ipswich River Wildlife Sanctuary in Massachusetts (Martin 2000). No information could be found about the areas invaded in Wisconsin, but it is likely that they are natural areas.

Subrank I - Ecological Impact: High/Medium

1. Impact on Ecosystem Processes and System-wide Parameters:High/Moderate significance
Comments: Glyceria maxima can form huge stands in wetlands (Martin 2000), therefore reducing open water. It can also convert fast-flowing aerobic streams into partially anaerobic swamps (Howard 2007).

2. Impact on Ecological Community Structure:High/Moderate significance
Comments: Stems of Glyceria maxima can be 2.5 meters high (Martin 2000); in monocultures there would be little open area.

3. Impact on Ecological Community Composition:High/Moderate significance
Comments: Glyceria maxima starts its growth early in the spring giving it a competitive advantage over other species; it has the ability to form large monocultures due to this and its rapid vegetative growth (Martin 2000).

4. Impact on Individual Native Plant or Animal Species:High/Moderate significance
Comments: Glyceria maxima affects all species in the areas it successfully invades but there is no evidence that it impacts particular natives greater than any other.

5. Conservation Significance of the Communities and Native Species Threatened:High/Moderate significance
Comments: Glyceria maxima threatens wetlands (though it is unclear whether wetlands need to be disturbed to allow G. maxima to get a foothold) which are not intrinsically rare but they are more vulnerable to invaders than other communities.

Subrank II. Current Distribution and Abundance: Low/Insignificant

6. Current Range Size in Nation:Low significance/Insignificant
Comments: As of the year 2000, Glyceria maxima had been detected only at a few locations in Wisconsin and Massachusetts in the U.S. (Martin 2000). There may be other localized infestations such as the one in Snohomish County, Washington where it has been given the status Class A Noxious Weed by the Washington State Noxious Weed Control Board. It was also detected at one location in Illinois at Illinois Beach State Park in 2006 (Howard 2007). It also occurs in Alaska and has invaded many areas in Ontario with additional stands in British Columbia and Newfoundland (Howard 2007).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:Low significance/Insignificant
Comments: Quick control action has prevented Glyceria maxima from impacted the areas of the U.S. where it has invaded (Martin 2000).

8. Proportion of Nation's Biogeographic Units Invaded:Low significance

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Low significance
Comments: Glyceria maxima invades freshwater wetlands and riparian habitats; in its native range it grows in reed swamps, lakes, ditches, riparian habitats, and ponds (Weber 2003).

Subrank III. Trend in Distribution and Abundance: Medium

10. Current Trend in Total Range within Nation:Medium/Low significance
Comments: Glyceria maxima was first found in the U.S. in the 1970's in a few locations in Wisconsin; it then appeared in the 1990's in Massachusetts, and has been found in Washington and Illinois in 2005 and 2006 (Howard 2007). Its range in the U.S. does not appear to be rapidly spreading, possibly due to rapid action taken upon detection.

11. Proportion of Potential Range Currently Occupied:High significance
Comments: Glyceria maxima seems capable of occupying wetland habitat throughout the U.S., though it has currently been detected in only a few widely separated areas.

12. Long-distance Dispersal Potential within Nation:High/Moderate significance
Comments: The seed and small sections of rhizomes of Glyceria maxima may be spread on water, in mud on machinery and vehicles, on footwear and on livestock (Tasmanian Department of Primary Industries and Water 2002) which makes it quite capable of long distance dispersal.

13. Local Range Expansion or Change in Abundance:Low significance
Comments: Glyceria maxima is not reported to be increasing in abundance within its current non-native range in the U.S.

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:Medium/Low significance
Comments: Glyceria maxima prefers well-aerated water with growth slowing as conditions become more anaerobic (Tasmanian Dept. of Primary Industries and Water 2002) which suggests it does not invade intact, vegetated wetlands; recently however G. maxima has been found to infest roadsides without standing water in Tasmania (Tasmania DPIW 2002) which does not suggest that it invades intact communities, but is evidence that the species is not restricted to open water.

15. Similar Habitats Invaded Elsewhere:Moderate significance
Comments: Glyceria maxima mostly invades wetland communities where ever it is reported to occur; however there is report of occurring in non-flooded roadsides in Tasmania which suggests it may not be restricted to wetlands.

16. Reproductive Characteristics:High significance
Comments: Glyceria maxima produces large numbers of seeds which have varying levels of dormancy with the majority germinating immediately but some remaining dormant for several years; seedlings quickly generate an extensive mat of roots and rhizomes which can then break off and spread vegetative growth further (Tasmanian DPIW 2002). A single rootstock may cover 25 square meters in 3 years; trailing stems growing in water produce roots and lateral shoots abundantly (Weber 2003).

Subrank IV. General Management Difficulty: High/Medium

17. General Management Difficulty:High/Moderate significance
Comments: Glyceria maxima's extensive rhizome system can quickly re-establish a population making removal difficult; scattered plants can be dug out but all rhizomes must be removed; glyphosate applied when the plant is in full flower has been effective (Weber 2003; Tasmanian DPIW 2002).

18. Minimum Time Commitment:High/Moderate significance
Comments: Because complete removal of rhizomes in water environments can be difficult and rhizomes can move into the site from adjacent sites via water, multi-year treatments of a site would likely be necessary.

19. Impacts of Management on Native Species:High/Moderate significance
Comments: Removal of the species by removing rhizomes is likely to have a significant impact on the ecology of an area; use of glyphosate may create less impact if applied carefully only to the target species.

20. Accessibility of Invaded Areas:Moderate significance
Comments: Glyceria maxima is likely to invade water habitats which can be difficult to access.
Authors/Contributors
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Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Anderson, J.E., and A.A. Reznicek. 1994. New England Note. Glyceria maxima (Poaceae) in New England. Rhodora 96(885): 97-101.

  • Barkworth, M.E., L.K. Anderton, K.M. Capels, S. Long, and M.B. Piep (editors). 2007. Manual of grasses for North America North of Mexico. Intermountain Herbarium and Utah State University Press, Logan, Utah. 627 pp.

  • Catling, P.M., and G. Mitrow. 2005. A prioritized list of the invasive alien plants of natural habitats in Canada. Canadian Botanical Association (CBA / ABC) Bulletin 38(4): 55-57.

  • Dore, W.G. 1947. Glyceria maxima in Canada. Canadian Field-Naturalist 61:174.

  • Dore, W.G. and J. McNeill. 1980. Grasses of Ontario. Monograph 26, Agriculture Canada, Research Branch, Biosystematics Research Institute, Ottawa, Ontario. 566 pp.

  • Douglas, G.W., D. Meidinger, and J. Pojar, eds. 2001b. Illustrated Flora of British Columbia, Vol. 7, Monocotyledons (Orchidaceae through Zosteraceae). B.C. Minist. Sustainable Resour. Manage., and B.C. Minist. For. Victoria, BC. 379pp.

  • Gutteridge, R.L. 1954. Glyceria maxima on the Mississippi River, Ontario, 1953. The Canadian Field-Naturalist, 68:133-135.

  • Howard, V.M. 2007. Glyceria maxima. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Revision Date: 6/15/2007.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Lambert, J.M. 1947. The Biological flora of the British Isles. Glyceria maxima (Hartm.) Holmb. L.C. (Ed. 11). No. 2190. Journal of Ecology 34:310-44.

  • Martin, T. 2000. Weed Alert! Glyceria maxima (C. Hartm.) Holmb. (Reed sweetgrass). The Nature Conservancy Global Invasive Species Initiative. Online. Available: http://tncweeds.ucdavis.edu/alert/alrtglyc.html (Accessed 2007).

  • Morse, L.E., J.M. Randall, N. Benton, R. Hiebert, and S. Lu. 2004. An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for Their Impact on Biodiversity. Version 1. NatureServe, Arlington, Virginia.

  • Tasmanian Department of Primary Industries and Water. 2002. Glyceria, Reed Sweet Grass (Glyceria maxima - Poa aquatica [Hartm.] Holmb) Control Guide. Available online: http://www.dpiw.tas.gov.au/inter.nsf/WebPages/RPIO-4ZV7D8?open Accessed Sept. 2007.

  • USDA, Natural Resources Conservation Service, PLANTS Database [USDA PLANTS]. http://plants.usda.gov/. Accessed 2007.

  • University of Wisconsin, Stevens Point Robert W. Freckmann Herbarium. No date. Plants of Wisconsin. Available: http://wisplants.uwsp.edu/index.html. (Accessed 2007).

  • Weber, E. 2003. Invasive plant species of the world: a reference guide to environmental weeds. CABI Publishing, Cambridge, Massachusetts. 548 pp.

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