The maidenhair spleenwort (Asplenium trichomanes) is a beautiful, dark-stemmed fern that can often be seen growing in the cracks of rock walls.
The maidenhair spleenwort is very demanding in regard to its habitat, preferring limestone rocks, due to which it is found in only a few locations in Helsinki. It is often difficult to spot, as it tends to hide in hollows and cavities. The only place in Helsinki where it is easy to observe is in Mustavuori, where it grows on rocks located right by a hiking trail.
Photo Teemu Saloriutta.