Another Carex new to the Netherlands has been recorded: I C. paniculala L. subsp. lusitanica (Schkuhr) Maire. Formerly known only from Portugal and Northwest-Africa, it has now been found in a wood planted on clay soil near Zwartsluis in the province of Overijssel. Several new hybrids are discussed and a key is given to the eight hybrids in subgenus Vignea. Special attention is given to the distribution and the habitats of the hybrids in the Netherlands. Hybrids seem to occur where there are changes in the quality of water and their presence can be used as an indicator of this process. From this, the occurrence of an hybrid population is deemed to result at a particular moment, representing a precise point during such change. Such processes, which are not reversible, appear to promote the germination of hybrid seeds from the seedbank in the soil. In the Netherlands, these processes – such as pumping water from greater depths and the artificial introduction of water from the Rhine to the Pleistocene areas – are rather widespread, such that the occurrence of hybrids is enhanced.