The Forest Law (Metsälaki) sets aside some forest sites. Lush & wet fern dominated swamps are such among others (lehtokorpi).
That's Athyrium filix-femina mainly here. Yrttikorpi, Somero, SW Finland. Plagiomnium undulatum, Sphagnum warnstorfii, Paludella squarrosa,
Carex loliacea, Below: Another lehtokorpi -site with lindens bending over the stream (Artjärvi S Finland).