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Wetland Plants and Plant Communities of Minnesota and Wisconsin


(Glyceria grandis S. Watson)

GRASS FAMILY (Gramineae or Poaceae)


FIELD CHARACTERISTICS: A perennial grass with stems growing to a height of 15 dm. The inflorescence is a large panicle 2-4 dm. long. The leaves are 8-12 mm. wide. Spikelets each have 5-9 flowers. The lemmas are distinctly 7-ribbed and are usually purple. In flower from June to August.

Giant manna grass can be easily distinguished from rattlesnake manna grass (Glyceria canadensis). Rattlesnake manna grass has smooth lemmas unlike the strongly nerved or ribbed lemmas of giant manna grass. Additionally, spikelets of rattlesnake manna grass are 3-5 mm. wide at maturity compared to the less than 2.5 mm. wide spikelets of giant manna grass.

Giant manna grass
Figure 15 - Giant Manna Grass

Illustrations by Elsie Froeschner in The Grasses of Iowa by Richard Pohl, Vol. 40, No. 4 (May 1966), of the Iowa State Journal of Science. Used herein with permission from the Iowa State University Press, Ames, Iowa.

Good field characteristics that aid in distinguishing the manna grasses (Glyceria spp.) in general from other grasses are the parallel ribs on the lemmas (use 10-15X magnification), and their frequently closed leaf sheaths.

ECOLOGICAL NOTES: Giant manna grass is found in shallow and deep marshes, fresh (wet) meadows, and bogs; commonly in shallow water.

SOURCE: Gleason and Cronquist (1991); and Voss (1972).

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