Crandon Ribbed Fen features a patterned peatland community - a unique wetland type that contains a series of peat ridges (strings) and hollows (flarks) oriented parallel to the slope of the landform and perpendicular to the flow of groundwater. The strings vary in height, width, and spacing, but are generally less than one meter tall, resulting in a faint wave-like pattern that may be discernable only from aerial photographs. The flarks are saturated to inundated open lawns of sphagnum mosses, sedges, and rushes, while the strings are dominated by sedges, shrubs, and scattered, stunted trees. Within a patterned peatland the peat "landforms" differ significantly in nutrient availability and pH, which influences the assemblage of plant species. The fen itself is surrounded by a narrow band of open black spruce swamp and embedded in a large area of black spruce swamp. The northern portion is a very wet, floating mat with springs and creeks. The southern end features distinctive patterning and varies from wet floating to firm with water-filled pools and strings, and wet to dry and crunchy flarks. Characteristic ribbed fen species include muck sedge, few-seeded sedge, white beak rush, sundews, horned bladderwort, and yellow-eyed grass. Patterned peatlands are only found at higher temperate and near-boreal latitudes of the northeastern and north-central United States and adjacent Canada. Crandon Ribbed Fen is owned by the DNR and was designated a State Natural Area in 2008.
