Royal Fern is one of the largest ferns in non-tropical North America. The spore-producing inflorescence at the top of the plant resembles groups of flowers, hence one of its other common names, Flowering Fern. Osmunda regalis creeps slowly by rhizomes, making it one of the slowest spreading ferns. Does best in acid soils, and grows slowly when planted in neutral or alkaline soil. Hardy to Zones 3 - 10.