Cystopteris laurentiana

St. Lawrence Bladderfern

St. Lawrence Bladderfern, Photo courtesy Wisconsin State Herbarium and Robert W. Freckmann><!-- #EndEditable --><!-- #BeginEditable
St. Lawrence 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.
  • laurentiana, for the St. Lawrence River and surrounding region
  • Common name from its range.
  • Other common names include Cystoptère Laurentienne (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: 17483
  • Also known as Cystopteris fragilis var. huteri, Cystopteris fragilis var. laurentiana
  • Cystopteris laurentiana is a sexual allohexaploid species with Cystopteris bulbifera as the diploid parent and Cystopteris fragilis as the tetraploid.
  • Sterile hybrids of Cystopteris laurentiana and Cystopteris fragilis have been identified where the two species occur together.
  • Previously thought to be common only in the Great Lakes region (hence the name) it is now known to occur frequently in the Driftless Area of the Midwest.


  • A small, lacy, deciduous fern of rocky places.
  • Fronds monomorphic, to 18", nearly all bearing sori.
    • Petiole (leaf stalk) shorter than blade; usually dark at base, grading to straw-colored; sparsely scaly at base.
    • Blade ovate to narrowly ovate, thrice-cut and lacy, widest above base; rachis and leaf ribs usually sparsely covered with tiny hairs, occasionally with misshapen bulblets.
    • Pinnae (primary leaflets) typically perpendicular to rachis, not curving toward blade tip, edges toothed. Veins directed into teeth and notches.
  • Rookstalk creeping, not cordlike, internodes very short, less than 5 mm, heavily beset with old petiole bases, scales uniformly brown.
  • Sori on underside of leaflets
    • Indusia cup-shaped, typically with sparse hairs.
    • 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 Fragile Fern, Cystopteris fragilis and Upland Brittle Bladderfern (Cystopteris tenuis) by its occasional hairs and bulblets, with fronds widest at or near the base.
    • Distinguished from Bulblet Fern, Cystopteris bulbifera by frond axis and leaflet ribs only sparsely covered with hairs, by occasionally bearing bulblets (often misshapen), and by nearly all leaves bearing sori. The frond axis and leaflet ribs of Bulblet Fern are densely covered with hairs; it will frequently bear bulblets and all but the earliest fronds of the season will bear sori.
  • Found only in Cook and Lake Counties in our area.
  • Field Marks
    • presence and density of hairs
    • presence and abundance of bulblets
    • abundance of sori


  • Ontario to Newfoundland, south to Iowa, Illinois, Pennsylvania, and Vermont.


  • Cracks and ledges on cliffs, often on calcareous substrates






  • By spore and vegetatively by rhizome.


  • By rhizome division.


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



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Last Updated on 26 February, 2004