Cystopteris tenuis

Upland Brittle Bladderfern

Upland Brittle Bladderfern, Photo courtesy Wisconsin State Herbarium and Robert W. Freckmann><!-- #EndEditable --><!-- #BeginEditable
Upland Brittle Bladderfern
Photo courtesy Wisconsin State Herbarium
and Robert W. Freckmann

Flora, fauna, earth, and sky...
The natural history of the northwoods


  • Cystopteris, from the Greek, kustis (cystis), "bladder" and pteris (pteris), "fern", a reference to the inflated indusia of these ferns.
  • tenuis, from the Latin, "slender"
  • Common name from
  • Other common names include Brittle Bladder Fern, Mackay's Brittle Fern, Cystoptère ténue (Qué)


  • Kingdom Plantae, the Plants
    • Division Polypodiophyta, the True Ferns
      • Class Filicopsida
        • Order Polypodiales
          • Family Dryopteridaceae, the Wood Ferns
            • Genus Cystopteris, the Bladder Ferns
  • Taxonomic Serial Number: 501961
  • Also known as Cystopteris fragilis var. mackayi, Nephrodium tenue


  • A small, deciduous fern of rocky places.
  • Fronds monomorphic, clustered at rootstalk crown, nearly all bearing sori; 6"-12" tall.
    • Petiole (leaf stalk) shorter than or nearly equal to blade length, dark at base, mostly green to straw-colored at upper end, base sparsely scaly.
    • Blade lanceolate to narrowly elliptic, once to twice cut, widest at or just below middle; axis and leaf ribs lacking hairs or bulblets; axils of pinnae lacking hairs.
    • Pinnae (primary leaflets) typically at acute angle (<90º) to leaf axis, often curving toward blade tip. Veins directed into teeth and notches.
    • Pinnules (secondary leaflets) lobed, looking rather like tiny oak leaves.
    • Indusia ovate to cup-shaped, without hairs.
  • Rootstalk creeping, not cordlike, internodes short, beset with old petiole bases, hairs absent; scales tan to light brown.
  • Spores spiny.


  • Identifiable as a Bladder Fern by thrice-cut, lacy fronds and rocky habitat.
  • WARNING: Cystopteris species are distinguished from one another with great difficulty and often not a little bit of frustration. The "distinguishing" characteristics are often difficult to identify clearly and there is a fair amount of overlap. That said:
    • Distinguished from Bulblet Fern, Cystopteris bulbifera, and St. Lawrence Bladder Fern, Cystopteris laurentiana by the absence of hairs and bulblets and by fronds widest at or just below the middle of the blade.
    • Distinguished from Fragile Fern, Cystopteris fragilis, by having pinnae at an acute angle (less than 90°) to axis, and often curving toward the blade tip.
  • Field Marks
    • shape of frond
    • absence of hairs and bulblets
    • angle of pinnae to stem


  • Minnesota to the Maritimes, south to Oklahoma, Arkansas, Tennessee, and North Carolina. Also Nevada, Utah, and Arizona.


  • Mostly on shaded rock and cliff faces but also occasionally on forest floors
  • Shady rock or cliff-faces, forest floors, lower altitudes.






  • By spore and vegetatively by rhizome.


  • By rhizome division.


  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Not generally available commercially.



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Last Updated on 26 February, 2004