Invasive Species: Glyceria maxima, Reed Mannagrass
Reed mannagrass is an invasive perennial, semiaquatic, rhizomatous grass. Stems are unbranched and can reach 2 to 8.2 ft. (0.6 to 2.5 m) in height. Leaves are 12 to 23.6 in. (30 to 60 cm) long and 0.2 to 0.8 in. (6 to 20 mm) wide, with acute apexes and prominent midribs. Flowering occurs in June to August, when flowers appear in panicles that are 6 to 12 in. (15 to 30 cm) long. Dark brown seeds develop throughout summer and autumn. This plant reproduces primarily vegetatively and occurs in sunny to semi-shady wetlands, where it can form dense, impenetrable stands. Reed mannagrass is native to northern Eurasia and was first found in North America in 1940 on the edge of Lake Ontario.
What are invasive species, and why should we be concerned about them?
Taxonomy: Scientific and Common Names for This Species
Cyperales > Poaceae > Glyceria maxima (Hartman) Holmb.
Synonyms: reed sweetgrass
Glyceria maxima - USDA PLANTS Profile
Distribution Maps
reed mannagrass - The reported distribution of this invasive species across the United States (Source: Invasive Plant Atlas of the United States)
Up-to-the-minute distribution maps and why they are important
Reporting This Invasive Species
What is the best way to report the occurrence of an invasive species?
How to report an invasive species sighting to EDDMapS - Early Detection & Distribution Mapping System
EDDMapS - Report an invasive species to EDDMapS.
County Extension Offices - Find your county Extension office on this map provided by USDA.
How to Identify
This invasive species can be identified by looking for the characteristics described in the paragraphs that follow.
Grass
Reed mannagrass is a perennial, semiaquatic, rhizomatous grass. Stems are unbranched and can reach 2 to 8.2 ft. (0.6 to 2.5 m) in height.
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| Robert Videki, Doronicum Kft., bugwood.org | bugwood.org |
Foliage
Leaves are 12 to 23.6 in. (30 to 60 cm) long and 0.2 to 0.8 in. (6 to 20 mm) wide, with acute apexes and prominent midribs.
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| Robert Videki, Doronicum Kft., bugwood.org | bugwood.org |
Flower
Flowering occurs in June to August, when flowers appear in panicles that are 6 to 12 in. (15 to 30 cm) long.
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| Leslie J. Mehrhoff, University of Connecticut, bugwood.org | bugwood.org |
Fruit
Dark brown seeds develop throughout summer and autumn.
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| Leslie J. Mehrhoff, University of Connecticut, bugwood.org | bugwood.org |
Native Species That Resemble Reed Mannagrass
- Images at invasive.org
| bugwood.org | bugwood.org |
- Images at invasive.org
| bugwood.org | bugwood.org |
Additional Images for Reed Mannagrass
reed mannagrass - Images at invasive.org
Learning Resources for Reed Mannagrass
Additional Information, Biology, Control and Management Resources
Control and management recommendations vary according to individual circumstances. Location, habitat, weather, and a variety of other conditions are factors that help determine the best treatment choice. To find the safest and most effective treatment for your situation, consult your state's land-grant institution. If you will use chemicals as part of the control process, always refer to the product label.
United States Land Grant University System - Find your Land Grant University's College of Agriculture, University Cooperative Extension Service, or other related partner on this map provided by USDA.
Glyceria maxima - Global Invasive Species Database
Weed Alert! - Global Invasive Species Team
Glyceria maxima - University of Connecticut
Glyceria maxima - The Nature Conservancy
Invasive Plant Atlas of New England - University of Connecticut
Invasive Species Compendium - cabi.org
