Cystopteris tenuis(Michx.) Desv.

upland brittle bladderfern

WFO wfo-0001110705 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 8 separate observations

Cystopteris tenuis, photographed by John Baur
fig. a John Baur, CC BY 4.0 / 2022-06-10 / obs. 204928133
Cystopteris tenuis, photographed by Elias
fig. b Elias, CC BY 4.0 / obs. 165879231
Cystopteris tenuis, photographed by Summit Metro Parks
fig. c Summit Metro Parks, CC BY 4.0 / obs. 185552214
Cystopteris tenuis, photographed by Micki Colbeck
fig. d Micki Colbeck, CC BY 4.0 / obs. 128017168
Cystopteris tenuis, photographed by er-birds
fig. e er-birds, CC BY 4.0 / obs. 80881729
Cystopteris tenuis, photographed by Dan Riley
fig. f Dan Riley, CC BY 4.0 / obs. 71231801
Cystopteris tenuis, photographed by Quinten Wiegersma
fig. g Quinten Wiegersma, CC BY 4.0 / obs. 38015281
Cystopteris tenuis, photographed by Étienne Lacroix-Carignan
fig. h Étienne Lacroix-Carignan, CC0 1.0 / obs. 117169960

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.

Native range 42 botanical countries

Regions where Cystopteris tenuis is native: Alabama, Arizona, Arkansas, Colorado, Connecticut, Delaware, District of Columbia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, Nevada, New Brunswick, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Nova Scotia, Ohio, Oklahoma, Ontario, Pennsylvania, Québec, Rhode I., South Dakota, Tennessee, Utah, Vermont, Virginia, West Virginia, Wisconsin AlabamaArizonaArkansasColoradoConnecticutIllinoisIndianaIowaKansasKentuckyLouisianaMaineMarylandMassachusettsMichiganMinnesotaMississippiMissouriNebraskaNevadaNew BrunswickNew HampshireNew JerseyNew MexicoNew YorkNorth CarolinaNova ScotiaOhioOklahomaOntarioPennsylvaniaQuébecSouth DakotaTennesseeUtahVermontVirginiaWest VirginiaWisconsin DelawareDistrict of ColumbiaRhode I.
Native distribution of Cystopteris tenuis, 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
Alabama ALA NORTHERN AMERICA
Arizona ARI
Arkansas ARK
Colorado COL
Connecticut CNT
Delaware DEL
District of Columbia WDC
Illinois ILL
Indiana INI
Iowa IOW
Kansas KAN
Kentucky KTY
Louisiana LOU
Maine MAI
Maryland MRY
Massachusetts MAS
Michigan MIC
Minnesota MIN
Mississippi MSI
Missouri MSO
Nebraska NEB
Nevada NEV
New Brunswick NBR
New Hampshire NWH
New Jersey NWJ
New Mexico NWM
New York NWY
North Carolina NCA
Nova Scotia NSC
Ohio OHI
Oklahoma OKL
Ontario ONT
Pennsylvania PEN
Québec QUE
Rhode I. RHO
South Dakota SDA
Tennessee TEN
Utah UTA
Vermont VER
Virginia VRG
West Virginia WVA
Wisconsin WIS

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 699 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -14.8 °C -9.2 °C -4.2 °C
Warmest month, mean daily high 22.8 °C 26.3 °C 28.9 °C
Annual rainfall 871 mm 1,144 mm 1,485 mm
Rainfall in the driest quarter 149 mm 236 mm 327 mm

It is found where winters bring hard frost. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 699 research-grade observations of Cystopteris tenuis 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 7 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.

  • Aspidium tenue (Michx.) Sw.
  • Athyrium tenue (Michx.) A.A.Eaton
  • Cystopteris filix-fragilis var. mackayi (G.Lawson) Farw.
  • Cystopteris filix-fragilis var. tenuis (Michx.) Farw.
  • Cystopteris fragilis var. mackayi G.Lawson
  • Nephrodium tenue Michx.
  • Polypodium tenue Hoffm.

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.