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For information on Wisconsin's natural communities, contact:
Ryan O'Connor
Natural Heritage Inventory Ecologist

Poor Fen

State Rank: S3     Global Rank: G3G4   what are these ranks?


Detailed Community Description from Ecological Landscapes of Wisconsin

General natural community overview

Counties shaded blue have documented occurrences for Poor Fen in the Wisconsin Natural Heritage Inventory database.

Poor fens are a weakly minerotrophic peatlands with the rooting zone in contact with surface water and/or groundwater. They often occur on the margins of "bog" lakes with a floating or grounded mat of peat and sedge rhizomes. They are frequently found in kettle depressions shallow depressions of glacial outwash and lakeplains. Nutrient availability is higher than in more acidic communities. Sphagnum mosses are common but don't typically occur in deep layers with pronounced hummocks. Floristic diversity is relatively high and may include white beak-rush (Rhynchospora alba), pitcher-plant (Sarracenia purpurea), sundews (Drosera spp.), pod grass (Scheuchzeria palustris), and the pink-flowered orchids (Calopogon tuberosus, Pogonia ophioglossoides and Arethusa bulbosa). Sedges are also common and include Carex oligosperma, C. limosa, C. lasiocarpa and C. chordorrhiza, as well as cotton-grasses (Eriophorum spp.).

Defining Characteristics and Similar Communities

Poor fens are distinguished by their weakly minerotrophic peatland soils influenced by surface and/or groundwater and relatively high species diversity. They are similar to open bogs, but have a higher pH, lack of pronounced leatherleaf and Sphagnum hummocks (often as high as two feet or more with intervening hollows in an open bog), and higher species diversity. In Wisconsin, these differences are all due to the fact that the vegetation in open bogs is slightly elevated above the influence of mineral-rich groundwater, usually by the growth and influence of Sphagnum hummocks, which despite wicking water upwards, actively acidify the rooting zone and cause nutrient availability to be extremely low. Poor fens may lie adjacent to muskegs, also known as treed bogs, but can be differentiated by typically having less than 10% cover of tree species.

Poor fens may be similar to northern sedge meadows in that both may be dominated by sedges, but sedge meadows usually lack calciphiles and have relatively few carnivorous plants and pink-flowered orchids. Poor fens may be distinguished from boreal rich fens by their lower pH, low abundance of strong calciphiles such as common bog-arrow grass (Triglochin maritima) and twigrush (Cladium mariscoides) and greater proportion of Sphagnum mosses. Poor fens often occur adjacent to Great Lakes shore fens, especially along the Lake Superior shoreline, and can be differentiated by their soils having slightly lower pH, higher coverage of Sphagnum moss (usually sparse in shore fens), and a grounded rather than floating mat not influenced by Great Lakes water levels. They also tend to have higher species diversity per unit area, perhaps due to the nutrient and elevation gradients provided by low Sphagnum hummocks. Poor fens may also resemble patterned peatlands, especially the minerotrophic hollows (flarks), but lack the patterning of alternating low ridges (strings) usually evident on aerial photos. Poor fens are also exceedingly more common than patterned peatlands.

Rare animals

Species of Greatest Conservation Need

Wisconsin Wildlife Action Plan graphic

The following Species of Greatest Conservation Need are listed according to their level of association with the Poor Fen natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.

Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.

Four-toed SalamanderHemidactylium scutatum3
Mink FrogLithobates septentrionalis2
Pickerel FrogLithobates palustris2

Ants, wasps, and beesScore
Frigid Bumble BeeBombus frigidus2

Cantrall's Bog BeetleLiodessus cantralli2

American BitternBotaurus lentiginosus3
Yellow RailCoturnicops noveboracensis3
American Black DuckAnas rubripes2
BobolinkDolichonyx oryzivorus2
Nelson's SparrowAmmodramus nelsoni2
Olive-sided FlycatcherContopus cooperi2
Rusty BlackbirdEuphagus carolinus2
Whooping CraneGrus americana2
Black-backed WoodpeckerPicoides arcticus1
Sharp-tailed GrouseTympanuchus phasianellus1
Short-eared OwlAsio flammeus1

Butterflies and mothsScore
Arctic FritillaryBoloria chariclea2

Dragonflies and damselfliesScore
Forcipate EmeraldSomatochlora forcipata3
Subarctic DarnerAeshna subarctica3
Zigzag DarnerAeshna sitchensis3
Incurvate EmeraldSomatochlora incurvata2
Ringed BoghaunterWilliamsonia lintneri2
Sphagnum SpriteNehalennia gracilis2

Grasshoppers and alliesScore
Bog ConeheadNeoconocephalus lyristes1
Delicate Meadow KatydidOrchelimum delicatum1
Spotted-winged GrasshopperOrphulella pelidna1

Leafhoppers and true bugsScore
A LeafhopperLimotettix elegans1
A LeafhopperLimotettix pseudosphagneticus1

Little Brown BatMyotis lucifugus2
Northern Long-eared BatMyotis septentrionalis2
Silver-haired BatLasionycteris noctivagans2
Big Brown BatEptesicus fuscus1
Tricolored BatPerimyotis subflavus1
Water ShrewSorex palustris1
Woodland Jumping MouseNapaeozapus insignis1

Eastern MassasaugaSistrurus catenatus3
Eastern RibbonsnakeThamnophis sauritus3
Blanding's TurtleEmydoidea blandingii1
Plains GartersnakeThamnophis radix1
Wood TurtleGlyptemys insculpta1

Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.

Rare plants

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.

Scores: 3 = "significantly associated," 2 = "moderately associated," and 1 = "minimally associated."
Scientific Name Common Name Score
Amerorchis rotundifolia Round-leaved Orchis 1
Carex exilis Coast Sedge 2
Carex michauxiana Michaux's Sedge 3
Drosera anglica English Sundew 3
Drosera linearis Linear-leaved Sundew 2
Eleocharis quinqueflora Few-flowered Spike-rush 1
Equisetum palustre Marsh Horsetail 3
Eriophorum russeolum ssp. leiocarpum Russet Cotton-grass 3
Juncus stygius Bog Rush 3
Pseudevernia consocians Common Antler Lichen 2
Rhynchospora fusca Brown Beak-rush 2
Salix sericea Silky Willow 1


The following Ecological Landscapes have the best opportunities to manage for Poor Fen, based on the Ecological Landscapes of Wisconsin Handbook.

Map of the Ecological Landscapes of Wisconsin.

Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.

Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.

Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.


Wisconsin Wildlife Action Plan graphic

What are conservation actions?

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for natural communities


Poor Fen Photos

Poor Fen Photo

Poor fen, Langlade County.

Photo by Emmet Judziewicz.

Poor Fen Photo

Poor fen in kettle bog, Bayfield County.

Photo by Eric Epstein.

Poor Fen Photo

Poor Fen dominated by Carex lasiocarpa with very wet Sphagnum lawns and small pockets of open water.

Photo by Ryan O'Connor.

Poor Fen Photo

Poor fen often occurs on saturated peat soils adjacent to lakes. Wild cranberries grow on Sphagnum moss hummocks, interspersed with cotton-grass.

Photo by Ryan O'Connor.

Poor Fen Photo

Tula Lake SNA with poor fen and black spruce swamp.

Photo by Amy Staffen.

Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.

Last revised: Tuesday, August 30, 2022