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Northern Oak Fern (Gymnocarpium jessoense ssp. parvulum)

Life history

Species overview

Northern Oak Fern (Gymnocarpium jessoense ssp. parvulum), a Wisconsin Special Concern plant, is found on dry to moist ledges of sandstone cliffs. The optimal identification period for this species is late May through late September.

Synonyms: Gymnocarpium jessoense


  • Distinguishing characteristics: Lower surface of frond and rachis densely and finely gladular-pubescent, upper surface of frond glabrous. Distinguished from G. robertianum by fronds which are glabrous on upper surface and fronds with the basal pinnae curved toward the tip of the blade rather than perpendicular to the blade.
  • Flower characteristics:
  • Fruit characteristics: Sori on the anterior vein branches, no indusium.
  • Leaf characteristics: Green blade, deltoid, to 14 cm long by 16 cm wide, though typically with the terminal third longer the than the two lower triangular pinnae; segments of the basal pinnae ovate-oblong, obtuse, sessile, curved toward the tip of the blade, with the lowest basal one mostly less than a fourth as long as the main rachis; lower frond surface and rachis densely and finely glandular-pubescent, but glabrous on the upper surface of the blade.


  • Blooming phenology:
  • Fruiting phenology:
  • Optimum time to identify: The optimal identification period for this species is late May through late September


  • Growth form: Fern
  • Vegetative reproduction: Rhizomatous
  • Life cycle: Perennial
  • Comments: Associated Species: Thuja occidentalis, Polypodium vulgare, Cystopteris fragilis, Phegopteris connectilis.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Northern Oak Fern (Gymnocarpium jessoense ssp. parvulum). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Gymnocarpium jessoense ssp. parvulum in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS1
Global RankG5T4T5
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found on dry to moist ledges of sandstone cliffs.
  • Soils: Moist, calcareous, rocky soils.

Natural communities

This table lists the natural communities that are associated with Northern Oak Fern. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Natural communities score
Dry Cliff 3
Moist Cliff 3

Ecological landscapes

This table lists the ecological landscape association scores for Northern Oak Fern. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Ecological landscape score
Central Sand Hills 2
Superior Coastal Plain 2

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • Avoid broadcast spraying of herbicides; use care with spot spraying.
  • Avoid direct disturbance to sensitive microsites such as seeps, cliffs, and moss-covered boulders.
  • Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • Buffer management around unique microhabitats such as ephemeral ponds, seeps, etc.
  • Follow BMPs, especially around streams and use care near ravines, steep slopes, cliffs, rock outcrops, etc.


Northern Oak Fern Photo.

Photo © Emmet Judziewicz.

Northern Oak Fern Photo.

Photo © Emmet Judziewicz.

Northern Oak Fern Photo.

Photo by Kevin Doyle, Wisconsin DNR.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition