Rusty-back Fern

The rusty-back fern (Asplenium ceterach) is a fern species in the spleenwort family Aspleniaceae, a perennial and evergreen plant with compact, intricately divided fronds up to 20 centimeters long. The undersides of its fronds are covered in a dense layer of pale reddish-brown scales, which give the species its common name, and the fronds curl up in summer to show just these scaly undersides. It is widespread across Europe, Asia, and North Africa, growing up to 2,700 meters above sea level in fissures of carbonate rock and on the mortar of stone and brick walls; unlike many ferns it thrives in full sun and needs little humidity. It is assessed as Least Concern by the IUCN.