rough mannagrass USDA PLANTS Symbol: GLMA3
U.S. Nativity: Exotic
Habit: Grass or Grasslike Aquatic Plants
Glyceria maxima (Hartman) Holmb.

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Taxonomic Rank: Liliopsida: Cyperales: Poaceae

Appearance
Glyceria maxima is a perennial, semi-aquatic, rhizomatous grass. Stems are unbranched and can reach 2-8.2 ft. (0.6-2.5 m) in height.
Foliage
Leaves are 12-23.6 in. (30-60 cm) long, 0.2-0.8 in. (6-20 mm) wide, with an acute apex and a prominent midrib. The leaf margins have stiff, short hairs. The leaf sheaths are rough in texture with a reddish-brown band at the leaf junction.
Flowers
Flowering occurs from June through August, when flowers appear in 6-12 in. (15-30 cm) long open panicles. The panicle branches have short, stiff hairs like those on the leaf margins.
Fruit
The small seeds are 0.06-0.08 in. (1.5-2 mm) long, obovoid in shape and smooth in texture. This plant reproduces primarily vegetatively through rhizomes.
Ecological Threat
Glyceria maxima occurs in sunny to semi-shady wetlands, where it can form dense impenetrable monocultures that crowd out native species. It is native to northern Eurasia and was first found in North America in 1940 on the edge of Lake Ontario.

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView All Images at Invasive.org


Flower(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Feature(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Feature(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Feature(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org
 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.


Invasive Listing Sources: