Synonymy

Caricetum rostratae Rübel 1912 p.p.; Caricetum acutovesicariae comaretosum Passarge 1955; Carex rostrata nodum Daniels 1978 p.p.

Constant species

Carex rostrata, Galium palustre, Menyanthes trifoliata, Potentilla palustris, Calliergon cordifolium/cuspidatum! giganteum.

Rare species

Carex appropinquata, C. aquatilis, C. diandra, Lysimachia thyrsiflora, Peucedanum palustre, Sium latifolium.

Physiognomy

The Potentillo-Caricetum rostratae comprises generally rather species-poor but somewhat varied mixtures of monocotyledons and herbaceous dicotyledons, sometimes developed as a floating mat. Among the monocotyledons, Carex rostrata is the most frequent species throughout but other sedges, such as C. vesicaria, C. nigra, C. elata and, more rarely, C. aquatilis and C. appropinquata, or Eriophorum angustifolium may each on occasion replace it as the dominant. In other cases, Phragmites australis or, less frequently, Juncus effusus or J. acutiflorus may dominate (see Sub-communities below).

A consistent feature of the community, however, is the presence of Potentilla palustris and Menyanthes trifoliata as an open or closed carpet beneath these usually taller species. They can occur in intimate mixtures or as patchy mosaics in which clumps of either attain local dominance and, scattered amongst them, is a variety of herbs, most commonly Galium palustre (which can sprawl extensively), Cardamine pratensis, Epilobium palustre, Mentha aquatica, Myosotis laxa ssp. caespitosa, Caltha palustris, Hydrocotyle vulgaris and Veronica scutellata. Taller species, such as Angelica sylvestris, Cirsium palustre and Valeriana officinalis, are sometimes conspicuous and there is a much greater variety of these in one of the sub-communities. In wetter places, Equisetum fluviatile may be abundant and, here too, there may be scattered clumps of Sparganium erectum or Typha latifolia. Agrostis stolonifera with, less frequently, some A. canina ssp. canina and Poa trivialis, can form extensive and. thick carpets, sometimes semi-submerged.

Almost always, one or more of the larger Calliergon spp., C. cuspidatum, C. cordifolium and C. giganteum, occur and these may form conspicuous patches over the mass of interweaving rhizomes and litter. No other bryophytes are frequent throughout but individual stands may have some Sphagnum squarrosum or S. fimbriatum or other locally abundant species.