Asplenium ruta-muraria & Asplenium trichomanes

Asplenium trichomanes L.

Perennial of the Aspleniaceae family, this fern with a circumboreal distribution is one of the most widespread of the genus: it is found on all continents, from temperate zones to subalpine regions, generally between sea level and 2,500 meters altitude. It colonizes rock crevices, shaded rock walls, old walls, and scree, on both calcareous and siliceous substrates depending on the subspecies.

It forms small, spreading, and persistent rosettes, 5 to 20 cm in height, immediately recognizable by their linear and pinnate fronds, bearing numerous oval to suborbicular pinnules, in a bright to medium green, regularly arranged on either side of a shiny, persistent dark brown-black rachis. This dark and shiny rachis, visible in the photograph where it contrasts sharply with the soft green of the pinnules, constitutes the most distinctive and elegant feature of the species.

The sori are oblong, arranged in rows on the underside of the pinnules. In its natural environment, sporulation extends from May to October. Several subspecies are recognized, differing notably by their calcicole or silicicole affinity.

In cultivation, it requires a well-drained substrate, exposure to shade or partial shade, and a certain ambient humidity. It naturalizes easily in wall crevices and shaded rock gardens, and withstands harsh winters without special protection.