Asplenium platyneuron aka Ebony Spleenwort

Asplenium platyneuron is a small fern that lives for years. Its common name is ebony spleenwort. It belongs to Aspleniaceae, the spleenwort family. It grows wild in eastern Canada and South Africa. Its native range also spans the central and eastern United States. It grows on wooded slopes, fields, and rocky banks. It also grows on ground that people have disturbed. Some Canadian provinces and US states list it as vulnerable or endangered.

Plants form small clumps with two kinds of fronds. Garden plants reach about 0.7–1.7 feet [0.2–0.5 metres] tall and wide. Short, pale green fronds arch out or hug the ground. These sterile fronds make no spores and stay green through winter. Taller, dark green fronds stand upright and bear spores. They die back in winter. Smooth, glossy stalks range from dark brown to black. The narrow frond blades grow slim toward both ends. Each has 15–45 pairs of leaflets along its main axis. The leaflets sit in turn on either side. These oblong leaflets have small teeth or round scallops along their edges. Each leaflet has a small lobe at its base. This lobe points toward the frond tip.

This fern makes neither flowers nor fruit. Sori, which hold spores, lie beneath the leaflets. They form paired rows that slant. Wind takes spores from the upright, fertile fronds. The plant can also form small buds near frond bases. These buds grow into new ferns when they reach soil. Gardeners can grow plants from spores or split up clumps. This fern can cross with other fern species in nature. Such crosses can yield sterile offspring that cannot breed.

Grow ebony spleenwort in part shade, in soil that drains well. It also copes with deep shade. Rocky soil, loam, and soil rich in organic matter suit it. It prefers acid soil but accepts neutral and alkaline soil. Guides suggest dry-to-medium soil or moist soil that drains well. The fern copes with drought, but wet ground can cause crown rot. Published US hardiness ranges span zones 3–8 and 3–9. The RHS gives it a UK rating of H5. Plants take about two to five years to reach full size.

Use it in shaded rock gardens, wall gaps, or woodland beds. Its small size suits pots and beds beneath shrubs. The fine fronds add texture but need little space. Deer and rabbits tend to leave it alone. It needs no routine pruning and has few serious health problems. Slugs and black fern aphids may still attack it. Soil that drains well helps prevent its main disease risk, crown rot.