This marsh type is dominated by Carex diandra, and often contains Menyanthes trifoliata and Potentilla palustris. It occupies fishpond littoral zones and depressions in mires with water slightly inundating the soil surface over most of the growing season. Soils are characterized by their high carbon content and extremely low concentration of nutrients compared to the other associations of the alliance Magno-Caricion elatae. In the Czech Republic this association is very rare; it has probably disappeared at some sites from where there are historical records.