De Naaldvarens (Polystichum-soorten) van het Overijsselse Hout bij Lelystad

The Overijsselse Hout, a deciduous forest planted twenty years ago on the outskirts of Lelystad, a town in one of the IJsselmeer polders, appears to harbour quite a number of fern species. Since 1979, 11 species have been recorded including Polystichum aculeatum (L.) Roth, P. setiferum (Forssk.) Woynar and even P. lonchitis (L.) Roth. The detection of the latter in 1987 appeared to be its second record in the Netherlands. All Polystichum specimens grow at the side of woodland ditches. The soil of the Overijsselse Hout forestry consists of very fine argillaceous sand and is rich in lime. In addition, the groundwater level in winter is rather high (40-60 cm below surface level). Obviously this combination of environmental conditions – shaded ditches in calcareous, humid soil – offers a suitable habitat for these montane ferns