Page author: Don Knoke
Glyceria grandis
American mannagrass

Distribution: Alaska south to Oregon, chiefly east of the Cascades; east to northeast United States and south to Virginia and New Mexico.

Habitat: Sloughs, damp meadows and stream borders.

Flowers: Late June - Early August

Origin: Native

Conservation Status: Not of concern


Strongly rhizomatous perennial, the culms 9-16 dm. tall.


Sheaths smooth, completely closed, or open up to 1 cm.; ligules 4-9 mm. long, obtuse, entire; blades flat, firm, 6-15 mm. broad.


Inflorescence a loose, open panicle 2-3.5 dm. long, the branches spreading, numerous; spikelets loosely 5- to 6-flowered, oblong in outline; glumes papery, lanceolate, 1-nerved, the first about 1.6-1.7 mm. long, the second, 2.5 mm. long; lemmas 2.5-2.7 mm. long, purplish, blunt, prominently 7-nerved to the scarious upper margin, the nerves non-convergent; paleas about equal to the lemmas, abruptly notched; stamens 3, or occasionally 2.

Accepted Name:
Glyceria grandis S. Watson

Synonyms & Misapplications:
Glyceria maxima (Hartm.) Holmb. ssp. grandis (S. Watson) Hultén
Glyceria maxima (Hartm.) Holmb. var. americana (Torr.) B. Boivin
Panicularia grandis (S. Watson) Nash
var. grandis – reed mannagrass
Additional Resources:

PNW Herbaria: Specimen records of Glyceria grandis in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Glyceria grandis checklist entry.

E-Flora BC: Glyceria grandis atlas page.

CalPhotos: Glyceria grandis photos.

USDA Plants: Glyceria grandis information.

27 photographs:
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