Pteris cretica and Adiantum raddianum (Pteridophyta) in light-shafts for cellars and water wells of the Ruhr area – subtropical fern taxa spreading in Germany?

Abstract

While conducting floristic surveys in towns of the Ruhr area, samples of Pteris cretica var. albolineata (Pteridaceae) and Adiantum raddianum (Adiantaceae), both treated s.l., in water wells and light-shafts for cellars were found. The growing places, population sizes and additional taxa are described. Questions about status and the propagation tendencies of the taxa are discussed.