Gymnocarpium dryopteris

Oak Fern

 Gymnocarpium dryopteris, Oak Fern
Oak Fern
Photo © by Earl J.S. Rook

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

Name:
  • Gymnocarpium, from the Greek, gumnos (gymnos), "naked", and karpos (karpos), "fruit"; a reference to the lack of indusia
  • dryopteris, from the Greek, drus (drys), "oak", pteris (pteris), "fern"
  • Common Name a translation of the Greek specific epithet
  • Other common names include Western Oak Fern, Gymnocarpe Fougère-du-chêne (Qué), Ekbräken (Swe), Fugletelg (Nor), Tredelt Egebregne (Dan), Metsäimarre (Fin), Þilaufungur (Is), Eichenfarn (Ger), Sgeamh Dharaich (Gaelic)

Taxonomy:
  • Kingdom Plantae, the Plants
    • Division Polypodiophyta, the True Ferns
      • Class Filicopsida
        • Order Polypodiales
          • Family Dryopteridaceae
            • Genus Gymnocarpium, the Oak Ferns
  • Taxonomic Serial Number: 17579
  • Also known as Dryopteris disjuncta, Dryopteris dryopteris, Dryopteris linnaeana, Lastrea dryopteris, Phegopteris dryopteris, Thelypteris dryopteris

Description:
  • A delicate, deciduous fern to 12" tall. Quite common in our North Woods.
  • Frond deciduous, lime-green, and broadly triangular.
    • Petiole (leaf stalk) very slender, shiny, straw-colored, sparsely scaly at base, usually longer than blades; 4"-12" long and parallel to the ground.
    • Blade broadly triangular in outline, 2"-7" long, 2"-5" wide, twice to thrice cut, and hairless; divided into three triangular, approximately equal divisions, each with 4-7 pairs of lobes or leaflets.
    • Sori small, circular dots on veins, near leaflet edges, lacking an indusium, hence Gymnocarpium
  • Rootstalk slender, creeping, blackish, with brown, fibrous scales.
  • Fiddleheads small and delicate, produced throughout the summer, in threes, corresponding to the three divisions of the frond.

Identification:
  • Identifiable as an Oak Fern by its small size, delicate form, and three lobed frond.
  • Distinguished from the closely related Northern Oak Fern (Gymnocarpium robertianum) by having its three frond segments more-or-less equal in size. The central lobe is significantly larger than the two side lobes in the Northern Oak Fern.
  • Distinguished from the Asian Oak Fern (Gymnocarpium jessoense) by the absence of glands on the smooth fronds.
  • Field Marks
    • small size
    • triangular, three-part frond
    • absence of glands on surface of frond

Distribution:
  • Circumboreal, Alaska to Newfoundland, south to Oregon, northern Idaho, NW Montana, Saskatchewan, Manitoba, Minnesota, Iowa, Wisconsin, Michigan, Ohio, West Virginia, and Maryland.
  • Scattered populations are found in the Black Hills and western mountains.

Habitat:
  • Moist to wet sites in cool, mixed conifer and northern hardwood stands; thickets, streambanks, and wet cliffs at low to moderate elevations.
  • Soils moist to well-drained, acidic, with pH of 4.5-6.4. Soil textures gravelly or sandy to silty clay loams.
  • Contrary to the common name, Oak Ferns do not grow on or near oak trees.
  • Common in Scotland where it is a component in the ground flora of the native Caledonian pine forests.

Fire:
  • Not considered a fire-surviving species but may sprout from rhizomes following light burns. Slow to return after major fire.
  • Spores are stored in soil seedbank, so fires that do not damage upper soil layers may not permanently eliminate Oak Fern from an area.

Associates:

History:
  • The Cree crushed the leaves to repel mosquitoes and soothe mosquito bites.

Uses:
  • Suitable for the shade garden.

Reproduction:
  • By spores and vegetatively by rhizomes
  • Spores well adapted for high wind dispersal

Propagation:
  • By rhizome division.

Cultivation:
  • Hardy to USDA Zone 2 (average minimum annual temperature -50ºF)
  • Cultural Requirements
    • Shade
    • Moist, organic soil
    • Fertilization unnecessary
  • Good for a low and delicate ground cover in shady locations.
  • Available by mail order from specialty suppliers.
  • Spreads by rhizome to form small patches.

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Last Updated on 26 February, 2004