Asplenium ceterach aka Rusty Back

Asplenium ceterach is an evergreen fern in the Aspleniaceae family. Gardeners know it as rustyback fern or scaly spleenwort. Its range covers Europe, North Africa and western Asia. It is native to Britain and Ireland. In the wild, it grows on limestone rocks and mortared walls. These sites suit its rock-dwelling way of life.

Short, upright rhizomes produce small tufts of narrow, lance-shaped fronds. The upper surface is dark green. Rust-brown scales cover the underside and give the fern its common name. Plants stand about 0.5 feet [0.15 metres] tall. Fronds can reach about 0.7 feet [0.2 metres] long. The RHS gives a broader garden height and spread range. Both run from about 0.3–1.6 feet [0.1–0.5 metres]. Plants take two to five years to reach full size. The foliage stays green through the seasons.

Grow this fern in part shade with shelter from exposure. Choose soil rich in humus that drains well but stays moist. Add grit to help water pass through the root zone. Neutral soil suits it, though the RHS prefers alkaline conditions. Suitable soils include loam, sand and chalk. North-, east- and west-facing sites offer planting options. The RHS rates it H5 for UK hardiness. This covers winter lows near 5–14°F, or −15 to −10°C. PFAF lists USDA zones 7–10.

Its compact, tufted form suits rock gardens and wall-side beds. It also fits pots, courtyards and small garden borders. Planting beneath shrubs offers another use in shaded gardens. PFAF suggests woodland edges and sites with dappled shade. The RHS reports few routine pest or disease problems. Remove dead or damaged fronds when needed. Divide plants to make more, or sow freshly ripe spores. The RHS gives a spore-sowing temperature of 15°C.

PFAF records no known edible uses for this species. It lists traditional use of the whole plant for coughs and urinary complaints. These uses do not establish that home treatment is safe. PFAF notes that medicinal use has not been fully tested. It reports no species-specific cases of toxicity. Its broader warning about hazards in some ferns does not prove this species is toxic. The evidence therefore does not establish either toxicity or food safety.