Verleden en heden van IJzervaren (Cyrtomium falcatum (L.f.) C.B.Presl.) in Nederland

Cyrtomium falcatum is an ornamental fern species which is popular in horticulture. It is commonly grown as a houseplant in West Europe and as a garden plant in warmer areas. The species is native in the Palaeotropics, where it is distributed from southeastern Africa to China and Japan. It has been introduced in North America and Europe and subsequently naturalized locally. The species is hardy in areas where winter temperatures do not drop below -7°C to -12°C. In western Europe this area includes roughly Portugal (including the Azores), Northwest Spain, coastal areas of the British Isles, and the west coast of France, Belgium, and the Netherlands. In the Netherlands, the first record of Cyrtomium falcatum dates from 1915, when it was found as an adventitious species near Valkenburg in the province of Limburg. Most Dutch records, however, were made between 1945 and 1955. In this period, the species was usually found growing on walls in several cities in the western provinces of the country. After 1955, the species almost disappeared due to the cold winters of 1956 and 1963, but it survived on a few locations in the province of Zeeland. Since 1990, the species has been expanding in the Netherlands. Not only did it return to the northwestern part of the country, but it showed up in the eastern part as well (Delden, prov. Overijssel). On top of that it has also been found in the Flamish cities of Gent and Nieuwpoort. This recent expansion in range by the species in Belgium and the Netherlands might be related to the more favourable climatic conditions in the last decade, in particular the high temperatures in winter.