Glyceria grandisS.Watson

American MannagrassAmerican mannagrassReed manna grass

WFO wfo-0000873218 Accepted WFO 2026-06 8 photographs CC BY

Plate 1 figs. a–h · 8 separate observations

Glyceria grandis, photographed by aarongunnar
fig. a aarongunnar, CC BY 4.0 / 2020-06-15 / obs. 79794321
Glyceria grandis, photographed by mfeaver
fig. b mfeaver, CC BY 4.0 / obs. 48912448
Glyceria grandis, photographed by mfeaver
fig. c mfeaver, CC BY 4.0 / obs. 48912301
Glyceria grandis, photographed by Nolan Exe
fig. d Nolan Exe, CC BY 4.0 / obs. 110465592
Glyceria grandis, photographed by aarongunnar
fig. e aarongunnar, CC BY 4.0 / obs. 44854726
Glyceria grandis, photographed by Matt Lavin
fig. f Matt Lavin, CC BY 4.0 / obs. 154537348
Glyceria grandis, photographed by Matt Lavin
fig. g Matt Lavin, CC BY 4.0 / obs. 154603864
Glyceria grandis, photographed by aarongunnar
fig. h aarongunnar, CC BY 4.0 / obs. 24258368

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

The specimen a real sheet, in a real collection

Herbarium
The New York Botanical Garden
Accession
1747502
Filed as
Glyceria grandis S.Watson
Det. by
M. H. Nee 2012-01-01
Collected
M. H. Nee 2012-07-10
Origin
US
The sheet
View the digitised specimen (CC BY 4.0)

A real pressed plant, in a real collection, under the accession number above. Not an illustration of one. The holding institution does not serve this sheet’s image to third parties, so there is no photograph here. The record is real and the link goes to it. Where we hold no openly licensed sheet for a species this section is simply absent, and where a sheet never recorded who determined it, that field stays empty rather than being filled in. Roughly half of all herbarium sheets never recorded a determiner, which is ordinary.

Native range 50 botanical countries

Regions where Glyceria grandis is native: Alaska, Alberta, Arizona, British Columbia, California, Colorado, Connecticut, Delaware, Idaho, Illinois, Indiana, Iowa, Maine, Manitoba, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Montana, Nebraska, Nevada, New Brunswick, New Hampshire, New Jersey, New Mexico, New York, Newfoundland, North Carolina, North Dakota, Northwest Territories, Nova Scotia, Ohio, Ontario, Oregon, Pennsylvania, Prince Edward I., Québec, Rhode I., Saskatchewan, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming, Yukon AlaskaAlbertaArizonaBritish ColumbiaCaliforniaColoradoConnecticutIdahoIllinoisIndianaIowaMaineManitobaMarylandMassachusettsMichiganMinnesotaMississippiMontanaNebraskaNevadaNew BrunswickNew HampshireNew JerseyNew MexicoNew YorkNewfoundlandNorth CarolinaNorth DakotaNorthwest TerritoriesNova ScotiaOhioOntarioOregonPennsylvaniaPrince Edward I.QuébecSaskatchewanSouth DakotaTennesseeUtahVermontVirginiaWashingtonWest VirginiaWisconsinWyomingYukon DelawareRhode I.
Native distribution of Glyceria grandis, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows. Regions too small to draw at this scale are marked with a dot.
RegionTDWG codeContinent
Alaska ASK NORTHERN AMERICA
Alberta ABT
Arizona ARI
British Columbia BRC
California CAL
Colorado COL
Connecticut CNT
Delaware DEL
Idaho IDA
Illinois ILL
Indiana INI
Iowa IOW
Maine MAI
Manitoba MAN
Maryland MRY
Massachusetts MAS
Michigan MIC
Minnesota MIN
Mississippi MSI
Montana MNT
Nebraska NEB
Nevada NEV
New Brunswick NBR
New Hampshire NWH
New Jersey NWJ
New Mexico NWM
New York NWY
Newfoundland NFL
North Carolina NCA
North Dakota NDA
Northwest Territories NWT
Nova Scotia NSC
Ohio OHI
Ontario ONT
Oregon ORE
Pennsylvania PEN
Prince Edward I. PEI
Québec QUE
Rhode I. RHO
Saskatchewan SAS
South Dakota SDA
Tennessee TEN
Utah UTA
Vermont VER
Virginia VRG
Washington WAS
West Virginia WVA
Wisconsin WIS
Wyoming WYO
Yukon YUK

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Where it actually grows measured, from 300 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -19.3 °C -12.3 °C -6.4 °C
Warmest month, mean daily high 21.4 °C 24.5 °C 27.8 °C
Annual rainfall 391 mm 769 mm 1,248 mm
Rainfall in the driest quarter 37 mm 85 mm 249 mm

It is found where winters are severely cold. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 300 research-grade observations of Glyceria grandis that carry a coordinate, and this is the range those places actually span. The 5th and 95th percentiles are used rather than the minimum and maximum, because a single cultivated specimen in a heated conservatory should not widen a tropical plant's range to the Arctic.

This is not a hardiness zone. A USDA zone is the average annual extreme minimum temperature. The figure above is the mean daily minimum of the coldest month, which is a different quantity and is typically far warmer. Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one.

Also published as 15 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Glyceria americana (Torr.) Pammel
  • Glyceria arundinacea subsp. grandis (S.Watson) Tzvelev
  • Glyceria flavescens M.E.Jones
  • Glyceria grandis f. grandis
  • Glyceria grandis f. pallescens Fernald
  • Glyceria grandis var. grandis
  • Glyceria grandis var. komarovii Kelso
  • Glyceria hulteniana Á.Löve
  • Glyceria maxima f. pallescens (Fernald) B.Boivin
  • Glyceria maxima subsp. grandis (S.Watson) Hultén
  • Glyceria maxima var. americana (Torr.) B.Boivin
  • Glyceria maxima var. grandis (S.Watson) Breitung
  • Panicularia americana (Torr.) MacMill.
  • Panicularia grandis (S.Watson) Nash
  • Poa aquatica var. americana Torr.

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.