Investigations were conducted in the upper tract of the Kosa River valley and Lake Czaple (Zachodniopomorskie province). A total of 200 vascular plant species belonging to 69 families were recorded. Forty seven of the reported species are legally protected or are found on the lists of threatened and vanishing species (e.g. Achillea ptarmica, Asplenium trichomanes, Epipactis helleborine, Polypodium vulgare). The dominant role in the tree layer is played by Alnus glutinosa, Quercus robur and Fraxinus excelsior. In the shrub layer abundant specimens of Frangula alnus, Corylus avellana, Sambucus nigra and Viburnum opulus are found, along with self-sown F. excelsior, Acer pseudoplatanus and Picea abies. In the herbaceous layer the most commonly found species include Calamagrostis canescens and taxa from genus Carex. Reported species most frequently represent communities from the following classes: Alnetea glutinosae, Querco-Fageta, Quercetea robori-petraeae, Vaccinio-Piceetea, as well as Phragmitetea. It was found that the biggest number of species prefer positions with moderate light and semi-shaded positions on fresh and moist, organic and mineral soils.

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