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The Royal Fern - Osmunda regalis is one of just ten species of deciduous, clump-forming ferns within the genus. It is also the hardiest and as such is the one most commonly found under cultivation. In its natural habitat of woodland bogs and stream banks it can grow to an impressive 3.5 metres tall. However under cultivation it is more likely to reach an overall height and spread of just 1-1.5 metres.
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The pea-green fronds are broadly lanceolate and bipinnate. The outer fronds are sterile while the central fronds have barren lower pinnae (a leaflet or primary division of a pinnately compound leaf) and fertile upper pinnae. The fertile pinnae have no pinnules, and their veins are covered with spore capsules which turn brown when ripe and resemble the dead flowers of the Astilbe genus.The plant gradually builds up a mass of crowns and matted black roots 2-3 ft above the ground. Incidentally, the roots are often used as an ingredient in orchid compost under the name of osmunda fibre.
Come the autumn the foliage will turns attractive red-brown colour before dying back.
Plant pot grown plants during March or April, in full sun or semi-shade. They prefer a cool, moist, humus rich, acidic soil, and when planting keep the crowns at soil level. The royal fern is particularly useful in sites that are prone to waterlogging and will even tolerate alkaline soils so long as plenty of fibrous compost is dug into the soil before planting. Top dress with a humus rich mulch in the spring.