Calamagrostis inexpansaA.Gray

Northern ReedgrassMaui reedgrass

WFO wfo-0000857450 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 3 observations

This species has been photographed under an open licence only 3 times, so some figures below are different views of the same plant, taken on the same day, rather than different individuals. They are usually different parts of it: the leaf, the flower, the bark.

Calamagrostis inexpansa, photographed by Zihao Wang
fig. a Zihao Wang, CC BY 4.0 / 2020-10-04 / obs. 102119611
Calamagrostis inexpansa, photographed by Zihao Wang
fig. b Zihao Wang, CC BY 4.0 / obs. 102120293
Calamagrostis inexpansa, photographed by Kathleen Houlahan Chayer
fig. c Kathleen Houlahan Chayer, CC0 1.0 / obs. 94390526
Calamagrostis inexpansa, photographed by Alan Weakley
fig. d Alan Weakley, CC0 1.0 / obs. 88250913
Calamagrostis inexpansa, photographed by Zihao Wang
fig. e Zihao Wang, CC BY 4.0 / obs. 102120272
Calamagrostis inexpansa, photographed by Zihao Wang
fig. f Zihao Wang, CC BY 4.0 / obs. 102119646
Calamagrostis inexpansa, photographed by Zihao Wang
fig. g Zihao Wang, CC BY 4.0 / obs. 102120318
Calamagrostis inexpansa, photographed by Zihao Wang
fig. h Zihao Wang, CC BY 4.0 / obs. 102120337

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
04310445
Filed as
Calamagrostis inexpansa A.Gray
Det. by
not recorded on this sheet
Collected
not recorded
Origin
not recorded
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 Calamagrostis inexpansa is native: Japan, Kamchatka, Kuril Is., Mongolia, Sakhalin, Alaska, Alberta, Aleutian Is., Arizona, British Columbia, California, Colorado, Connecticut, Idaho, Illinois, Indiana, Iowa, Kansas, Labrador, Maine, Manitoba, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Brunswick, New Hampshire, New Jersey, New Mexico, New York, Newfoundland, North Dakota, Northwest Territories, Nova Scotia, Nunavut, Ohio, Ontario, Oregon, Pennsylvania, Québec, Saskatchewan, South Dakota, Utah, Vermont, Washington, Wisconsin, Wyoming, Yukon JapanKamchatkaMongoliaSakhalinAlaskaAlbertaArizonaBritish ColumbiaCaliforniaColoradoConnecticutIdahoIllinoisIndianaIowaKansasLabradorMaineManitobaMichiganMinnesotaMissouriMontanaNebraskaNevadaNew BrunswickNew HampshireNew JerseyNew MexicoNew YorkNewfoundlandNorth DakotaNorthwest TerritoriesNova ScotiaNunavutOhioOntarioOregonPennsylvaniaQuébecSaskatchewanSouth DakotaUtahVermontWashingtonWisconsinWyomingYukon
Native distribution of Calamagrostis inexpansa, 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.
RegionTDWG codeContinent
Alaska ASK NORTHERN AMERICA
Alberta ABT
Aleutian Is. ALU
Arizona ARI
British Columbia BRC
California CAL
Colorado COL
Connecticut CNT
Idaho IDA
Illinois ILL
Indiana INI
Iowa IOW
Kansas KAN
Labrador LAB
Maine MAI
Manitoba MAN
Michigan MIC
Minnesota MIN
Missouri MSO
Montana MNT
Nebraska NEB
Nevada NEV
New Brunswick NBR
New Hampshire NWH
New Jersey NWJ
New Mexico NWM
New York NWY
Newfoundland NFL
North Dakota NDA
Northwest Territories NWT
Nova Scotia NSC
Nunavut NUN
Ohio OHI
Ontario ONT
Oregon ORE
Pennsylvania PEN
Québec QUE
Saskatchewan SAS
South Dakota SDA
Utah UTA
Vermont VER
Washington WAS
Wisconsin WIS
Wyoming WYO
Yukon YUK
Japan JAP ASIA-TEMPERATE
Kamchatka KAM
Kuril Is. KUR
Mongolia MON
Sakhalin SAK

Not drawn on the map: Kuril Is., Aleutian Is.. We hold no public-domain boundary for these regions, so they are listed rather than guessed at.

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 54 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -28.6 °C -17.2 °C -7.2 °C
Warmest month, mean daily high 15.7 °C 22.0 °C 28.0 °C
Annual rainfall 347 mm 855 mm 1,229 mm
Rainfall in the driest quarter 41 mm 141 mm 266 mm

It is found where winters are arctic. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 54 research-grade observations of Calamagrostis inexpansa 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 53 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.

  • Calamagrostis aculeolata (Hack.) Ohwi
  • Calamagrostis americana (Vasey) Rydb. & Shear
  • Calamagrostis breviseta var. lacustris Kearney
  • Calamagrostis californica Kearney
  • Calamagrostis canadensis var. arcta Stebbins
  • Calamagrostis chordorrhiza A.E.Porsild
  • Calamagrostis crassiglumis Thurb.
  • Calamagrostis elongata (Kearney) Rydb.
  • Calamagrostis expansa Rickett & Gilly
  • Calamagrostis fernaldii Louis-Marie
  • Calamagrostis hyperborea Lange
  • Calamagrostis hyperborea var. americana (Vasey) Kearney
  • Calamagrostis hyperborea var. elongata Kearney
  • Calamagrostis hyperborea var. hyperborea
  • Calamagrostis hyperborea var. stenodes Kearney
  • Calamagrostis inexpansa subsp. barbulata (Kearney) Piper & Beattie
  • Calamagrostis inexpansa var. barbulata Kearney
  • Calamagrostis inexpansa var. brevior (Vasey) Stebbins
  • Calamagrostis inexpansa var. cuprea Kearney
  • Calamagrostis inexpansa var. inexpansa
  • Calamagrostis inexpansa var. novae-angliae Stebbins
  • Calamagrostis inexpansa var. robusta (Vasey) Stebbins
  • Calamagrostis labradorica Kearney
  • Calamagrostis lacustris (Kearney) Nash

and 29 more.

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.