Asplenium ceterach

Asplenium ceterach, also known as Common Spleenwort or Rustyback, is a small evergreen fern species that grows spontaneously in the cracks of rocks and old limestone walls. It is recognisable by its long, narrow leaves that are divided into lobes and unfurl into crooks, forming dense rosettes. Relatively hardy and adapted to drought, this modest fern that lives on air will enhance all shaded areas where soil is scarce, such as crevices in walls and rocky areas where it self-seeds spontaneously.

Asplenium ceterach belongs to the Aspleniaceae family, which includes about 700 species of terrestrial ferns, as well as those that grow on tree branches (epiphytes) or rocks (lithophytes). Its distribution range includes Eurasia with mild winters and Mediterranean regions. It is a perennial plant with an erect rhizome, forming small, low, and spreading but very dense clumps, 15 cm (6 in) tall and 30 cm (12 in) wide. Each clump is composed of numerous fronds, or leaves. These elongated fronds, measuring 15 to 20 cm (6 to 8 in) in length, are divided into pinnae or entire lobes with an ovate to triangular shape, directly attached to the main vein called the rachis. Their undersides are covered with silvery scales that turn brownish-red. The fronds persist in winter but can dry out in summer during drought, curling up without harming the plant's survival. Their colour is light green when they unfurl in spring, becoming dark green later on. The reproduction of this fern is ensured by the production of sori, which are circular clusters of sporangia containing tiny spores. These sori, dark yellow to brown in colour, form in the middle of spring, on the undersides of the fronds. This Asplenium thrives in summer drought and on limestone substrates.

This small fern that thrives in shade or partial shade finds its place in rockeries, on top of walls, or even in the crevices of dry stone walls that rarely receive direct sunlight. It can also be grown in pots, in a very well-draining mixture enriched with gravel. In favourable conditions, it self-seeds everywhere, always in rock crevices, preferably in the shade, and never in arid areas. It often coexists with Ivy-Leaved Toadflax (Cymbalaria muralis), another wandering and robust plant. Plant it at the base of deciduous shrubs or along paths, in areas where the soil is poor and dry. You can also combine this Asplenium with epimediums or Cyclamen.

Common Spleenwort is also a medicinal plant that was once used to treat lung ailments. This fern is still used in herbal medicine.