Osmunda regalis aka Royal Fern

Osmunda regalis, or royal fern, belongs to the Osmundaceae family. It is a perennial fern that forms large clumps. Kew places its native range across Europe, the Mediterranean and Iran. It also includes Macaronesia, parts of Africa and nearby islands. The RHS lists it as native to Britain and Ireland. Wild plants grow in bogs, fens and damp woods. They also grow beside streams and on wet ledges.

Garden size varies with the site and the source. Missouri Botanical Garden gives heights of 2–3 feet [0.6–0.9 metres]. With steady moisture, plants can reach 6 feet [1.8 metres]. The RHS gives 5–8 feet [1.5–2.5 metres] for mature plants. Another source reports extremes near 10 feet [3 metres]. Clumps spread about 2–3 feet [0.6–1 metre]. A thick, upright rhizome supports the broad, arching fronds. Plants lose their leaves in cold winters. They may keep them where winters stay warm.

New fronds emerge pink, then turn green as they grow. Each bipinnate frond has two levels of leaflets. The leaflets sit well apart along the frond. Smaller leaflets have blunt or rounded tips and smooth edges. The rounded leaf stalk has a shallow groove. Stems range from brown to copper in colour. Autumn brings yellow, brown or red-brown leaves. Royal fern makes neither flowers nor fruit. Brown spore-bearing clusters form at the tips of fertile fronds. These explain its other name, flowering fern.

Grow it in cool, damp sites with some shade. Rich soil with plenty of humus suits it best. It prefers acid soil but can tolerate other conditions. The RHS allows alkaline soil with added fibrous compost. Clay, loam and sandy soils can all support it. Keep the soil moist; plants also tolerate very wet ground. Sun suits it where summers stay cool and water remains plentiful. Hot summer sun is less suitable. Sources give USDA zones 3–9 and UK hardiness H6. Growth is moderate, and care needs are low.

Use royal fern beside ponds, in rain gardens or shaded borders. Its clumps also suit woodland beds and mass plantings. The foliage gives small animals and birds shelter. Deer seldom damage it, and serious pests or diseases are uncommon. Remove dead or damaged fronds when needed. Divide plants in spring or autumn, or sow ripe spores. Its root fibre has served as a potting material for orchids. Sources also record past medicinal uses of roots and fronds. PFAF lists no known edible uses. It reports no species-specific toxicity, but this does not establish safety.