Rusty back fern
Synonym Asplenium ceterach
Epithet means "medicinal."
description: The rhizome is erect. Succulent tan-green stipes with a sparse smattering of brown scales are one-fourth the length of the frond or less. The rich green blades with zigzag lobes of pinnae are reminiscent in outline of the rick-rack that adorned the dresses of little girls in my childhood. Young fronds emerge with a shimmering undercoat of translucent and protective silvery scales. In time these mature to the rust color of the common name. Sori in a herringbone pattern with linear indusia are along veins and often concealed by the abundant cloak of scales.
range and habitat: The rusty back fern, when happy, is a photogenic inhabitant of sunny walls and crumbly crevices throughout Britain, Europe, North Africa, the Caucasus, Russia, and the Himalayas. Even in good health the pinnae tend to roll ever so slightly inwards exposing the seasonally appropriate skirt of silver to rust-colored scales. It will, however, curl tightly when drought stressed fully exposing the protective and water-collecting scales of its undersides. When moisture re-enters the scales and consequently the pinnae, the fern rejuvenates as a fresh rosette.
culture and comments: This and Asplenium ruta-muraria are among the most difficult ferns to introduce to cultivation. Acclimated plants are a magnificent sight indeed. The hands-down best that I have ever seen were in the garden of the late Mr. and Mrs. Hugh Baird of Bellevue, Washington, where a few plants were tucked into the top of a west-facing wall in full sun. To the envy of Mrs. Baird's fellow pteridomaniacs, sporelings cascaded down the wall joining the equally successful planting of Erinus alpinus. Give this fern coarse grit, a limey additive such as broken concrete chunks the size of marbles or smaller, and a sunny exposure. Beware the lime of lawns and avoid the occasionally recommended gypsum altogether. Do not overwater. Troughs, which give the gardener the opportunity and mobility to test various exposures, are an excellent option.
Subsp. bivalens is smaller with spores proportionately reduced in size, and the attractive 'Crenatum' has crenate (scalloped) margins.
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