Gymnocarpium jessoense
Northern oak fern
Image of Gymnocarpium jessoense

Photo by Emmet J. Judziewicz 

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Key Characteristics

Small fern (10-50 cm) of cool rocky outcrops in the west Upper Peninsula; leaf broadly triangular, twice-divided, lowest pinnae curved, arching to apex of leaf; underside of leaf and rachis densely covered by short, glandular hairs.

Status and Rank

  • State Status: E
  • State Rank: S1
  • Global Rank: G5


County NameNumber of OccurrencesYear Last Observed
Distribution map for Gymnocarpium jessoense

Updated 5/15/2018. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


Known from an igneous outcrop in the western Upper Peninsula. Elsewhere, this species occurs in acid to neutral substrates, including cool, shale talus slopes and also on granite cliffs and outcrops.

Natural Community Types


For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Associated Plants

The collection data indicate only that this species occurred with common oak fern.


A status survey is the primary need, as there is much potential habitat in Upper Michigan. Protection is likely best achieved by simply maintaining high quality outcrop habitats.

General Survey Guidelines

Random meander search covers areas that appear likely to have rare taxa, based on habitat and the judgement of the investigator.

Survey Methods

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at [Accessed Aug 18, 2018]


Survey References

Technical References

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