Boreal rich fen is a rare open peatland community of northern Wisconsin that is associated with glacial moraines, or less commonly, outwash landforms, in which the underlying substrate includes calcareous materials. Like many other northern peatlands, nutrient levels are low, but pH is significantly higher than in the poor fen and open bog communities and influences the plant composition. Sphagnum mosses are of lesser importance in this type than are the so-called "brown" mosses (e.g., from the genera Campylium, Drepanocladus, or Scorpidium). Characteristic vascular plants may include woolly sedge (Carex lasiocarpa), twig-rush (Cladium mariscoides), white beak-rush (Rhynchospora alba), beaked bladderwort (Utricularia cornuta), rushes (Juncus spp.), Hudson Bay cotton-grass (Scirpus hudsonianus), rush aster (Symphyotrichum boreale), and buckbean (Menyanthes trifoliata).
The most nutrient-rich boreal rich fens occur on the Door Peninsula, which is underlain by calcareous bedrock and mantled with calcareous till. Here, in addition to the species mentioned above, the open peatlands may support species such as coast sedge (Carex exilis), linear-leaved sundew (Drosera linearis), brook lobelia (Lobelia kalmii), grass-of-Parnassus (Parnassia glauca), shrubby cinquefoil (Dasiphora fruticosa), hair beak-rush (Rhynchospora capillacea), and tufted bulrush (Trichophorum cespitosum). The proximity of carbonate-enriched bedrock is almost certainly among the factors responsible for the composition of the boreal rich fens in this region.
Shrub phases of this community also occur, in which shrubby cinquefoil (Dasiphora fruticosa), bog birch (Betula pumila), sage willow (Salix candida), and speckled alder (Alnus incana) may be present in significant amounts, and collectively form the dominant plant cover.
