Ceterach officinarum

Perennial fern of the Aspleniaceae family, Ceterach officinarum is widespread from the Mediterranean basin to Central Asia and the Western Himalayas, with isolated populations in Atlantic and Central Europe. It colonizes rock crevices, old walls, limestone scree, and exposed rocky slopes, from sea level up to about 2,500 meters in mountainous regions.

It forms small, dense, and persistent rosettes, 5 to 20 centimeters high, with pinnately lobed, leathery, and arched fronds. The upper side of the fronds is dark green, while the underside is entirely covered with russet to golden brown scales, tight and overlapping, which completely mask the sporangia and give the plant its most characteristic appearance.

This scale covering is not just an ornament: it constitutes a remarkable adaptation to xerophytism. During drought periods, the fronds curl up on themselves, underside outwards, exposing their silvery-rust coating and drastically reducing water loss. The plant can thus survive almost complete desiccation and quickly green up again as soon as moisture returns.

In cultivation, it requires very well-drained soil, preferably limestone, in a sunny to semi-shaded exposure. It readily settles in the crevices of dry stone walls and does not tolerate excess winter moisture at the collar.