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A fen is a type of wetland fed by surface and/or groundwater. The flora of fens is characterized by their water chemistry. Fens are often confused with bogs, which are fed primarily by rainwater and often inhabited by certain sphagnum moss, making them acidic.

Contents 1 The characteristics of a fen 2 Linguistic issues 2.1 Derivation 2.2 Latin and place names 3 Fen flora 3.1 List of fen flora species 3.1.1 In pools 3.1.2 In typical fen 3.1.3 In fen carr 4 See also 5 References

Fens are characterize by their flora, which can include both Sphagnum mosses when pH is low and surface water dominates, or brown mosses when groundwater dominates.

The word fen is derived from Old English (fenn) and considered to have proto-Germanic origins, since it has cognates in Gothic (fani), Old Frisian (fenne), Dutch (veen) and German (Fenn(e), Venn; especially in the "Low German" language area: Vehn, Feen). In medieval Swiss German, gfenn.

In northern Europe, many of the natural fenlands lay in countries which have been densely populated for centuries. Nearly all the fens in England and the Netherlands, for example, had been drained before the people who knew about the wetlands wrote about them. Consequently, there is much confusion regarding the nomenclature of fens. This is particularly true because much of the written evidence from that time is in Latin, a language developed in the milder climate of southern Europe. Tidal marshes and bogs are uncommon near tideless seas, where the summers are rainless. These careful distinctions between habitats were noted by peasants, who thus developed knowledge of the various products obtainable from the wetland. However, the peasants' knowledge and experience went unnoticed by the scholars and lawyers who wrote about the fens. In these developed countries, it is, therefore, place names which remain as the main linguistic source of information about the distribution of the pre-drainage habitats.

The fen is a phase in the development of the natural succession from open lake, through reedbed, fen and carr, to woodland as the peat develops and its surface rises. Carr is the northern European equivalent of the swamp of the south-eastern United States. It is fen overgrown with generally small, trees of species such as willow (Salix spp.) or alder (Alnus spp.). A list of species found in a fen therefore covers a range from those remaining from the earlier stage in the successional development to the pioneers of the succeeding one.

Fen also merges into freshwater marsh where it develops more in the direction of grassland. This is most likely to occur where the tree species of carr are systematically removed by man for the development of pasture. This process can be hastened by partial drainage.

Particularly where the fen is fed by runoff from surrounding land, it is common for there to be strips of fen fed by the base-rich waters lying between 'islands' of bog which are fed by rainfall. Thus, there is plenty of opportunity for merging or juxtaposition of the floras typical of the different habitats.

The following is a list of plant species to be found in a north European fen with some attempt to distinguish between reed bed relicts and the carr pioneers. However, nature does not come in neat compartments so that for example, the odd stalk of common reed will be found in carr.

• Beaked sedge; Carex rostrata
• Whorl grass; Catabrosa aquatica
• Needle spike rush; Eleocharis acicularis
• Northern spike rush; Eleocharis austriaca
• The sweet grasses; Glyceria spp.
• Reed; Phragmites australis
• Swamp meadow grass; Poa palustris

• Flat sedge; Blysmus compressus
• Great fen sedge; Cladium mariscus
• Davall's sedge; Carex davalliana
• Dioecious sedge; Carex dioica
• Brown sedge; Carex disticha
• Slender sedge; Carex lasiocarpa
• Flea sedge; Carex pulicaris
• Common spike rush; Eleocharis palustris
• Few-flowered spike rush; Eleocharis quinqueflora
• Slender spike rush; Eleocharis uniglumis
• Broad-leaved cotton sedge; Eriophorum latifolium
• Brown bog [sic] rush; Schoenus ferrugineus

• Narrow small reed; Calamagrostis stricta
• Purple small reed; Calamagrostis canescens
• Cyperus-like sedge; Carex pseudocyperus
• Wood club rush; Scirpus sylvaticus

Bayou Biodiversity Action Plan Bog Marsh Mesopotamian Marshes

Salt marsh Slough Swamp Wetland

Rose, F. Grasses, Sedges, Rushes and Ferns of the British Isles and north-western Europe (1989) ISBN 0-670-80688-9