© A Klopper

Osmunda regalis is unusual in that it forms new fertile fronds in autumn, and not in spring or summer as is common in most ferns.

Description
Plants form huge, light green rosettes of up to 1.5 m high under favourable conditions. Young fronds (leaves) are covered in a hairy felt as they emerge, but become hairless at maturity. The bipinnate (doubly divided) fronds are lanceolate (lance-shaped and tapering towards the tip), rather leathery and can be as large as 600-1 200 x 300-450 mm. The elongated, blunt-tipped pinnules (leaflets) have serrated edges and turn from red to green as they mature.

The fertile pinnules at the tip of each fertile frond are narrowed, clustered and apparently totally covered with sporangia (spore-bearing structures). These sporangia, which are green when young, but darken to brown at maturity, are large and not in sori (clusters of sporangia).

The erect, fertile fronds in the centre of the plant project above the outer spreading, sterile fronds.

Plants have a massive creeping rhizome (root system) and the rootstock can protrude several centimetres above the ground like a short trunk covered with leaf sheaths and roots.

Distribution
Osmunda regalis is an almost cosmopolitan species. It occurs in Europe, North, Central and South America, Asia, Africa, Madagascar and the Mascarene Islands, but is not found in Australia or New Zealand. In southern Africa it is commonly found in the wetter regions and prefers areas with an annual rainfall of 400-1 200 mm per annum. It has a wide altitudinal range in southern Africa, occurring from near sea level to 2 000 m. The species is abundant in the warmer, low-altitude regions along the base of the Eastern Escarpment and becomes less frequent at higher altitudes. It often occurs in woodland and forest, but generally requires fairly high light intensity. It can form large colonies and always grows near water, along rivers and streambanks, where the rhizome is continually bathed in running water. It is less common in wet grasslands, in half to full shade, and is rarely found in open positions, on sand or gravel soils.

Derivation of name and historical aspects
The origin of this fern's name is too old to be traced. Possible derivations include the Saxon name 'Osmond' for the Germanic god Thor, or combining the Latin os (= mouth) and mundus (= clean), as it was reputedly used to clean the mouth. Another possibility is that it was named after King Osmund, who reigned over the South Saxons about 758 A.D. If this is true, the specific epithet regalis, meaning royal, would then be obvious. It may also refer to the fact that this species is very widespread in Europe, or to the stately growth of the plant.

The family Osmundaceae is an isolated and primitive group with no close relations. Osmundaceae fossils are known from as far back as the Permian (290-248 million years ago), while modern Osmunda fossils have been found in Upper Cretaceous sediments (up to 65 million years ago). The genus Osmunda comprises approximately seven species, of which only O. regalis, also the largest member of the genus, occurs in southern Africa. The only other representative of the family in southern Africa is Todea barbara.

Uses and cultural aspects
The rhizome of this plant was used as a remedy in Europe against rickets and abscesses. Patients also had to sleep on a bed made of the herbaceous parts of the plant. Poultices or emollients containing Osmunda regalis rootstock are reputedly an effective treatment for bruises, burns, sprains, broken bones and ulcers. The stem was used as an astringent and a tonic. When the root is slowly simmered in water it breaks down to a mucilaginous mass that was very popular for stiffening linen. The fibrous roots do not compact or soften easily and have long been used as a growing medium in the cultivation of orchids and other plants.

Growing Osmunda regalis


© A Klopper

Its large size, longevity and the distinctly different sterile and fertile parts make this slow-spreading species an ideal accent plant for landscaping. It is especially useful for waterside planting, but needs space to be fully appreciated. It grows well in shade, but tolerates full sun if it receives plenty of moisture and will thrive in wet, boggy soils. These ideal conditions should be matched as closely as possible when cultivating this species in the garden. Osmunda regalis requires a cold winter, and this is maybe the reason why, in southern Africa, this species tends not to form the massive plants (with fronds of up to 3.3 m in favourable conditions) seen in Europe. It also restricts the use of this fern as a houseplant.

The royal fern can be propagated by dividing the crown before the new spring growth uncoils and planting the divisions in well-prepared soil. Division must only be done when absolutely necessary and the wounds must be sealed to prevent fungus infection. This species prefers acid to neutral soil, rich in humus. A mixture of loam, sharp sand and leaf mould or peat can be added to the soil when preparing for planting. It can also be easily grown from spores. Bear in mind that Osmunda has green spores and these must be sown fresh. Viable spores germinate quickly, often within a day.

References

• BURROWS, J.E. 1990. Southern African ferns and fern allies. Frandsen Publishers, Sandton.
• FREETHY, R. 1987. British ferns. The Crowood Press, Wiltshire.
• JACOBSEN, W.B.G. 1983. The ferns and fern allies of southern Africa. Butterworths, Durban.
• JEFFERSON-BROWN, M. 1992. Hardy ferns. Ward Lock, London.
• JONES, D.L. Encyclopaedia of ferns. Timber Press, Oregon.
  PERL, P. 1979. The Time-Life encyclopaedia of gardening: ferns. Time-Life International, The Netherlands.
• ROUX, J.P. 2001. Conspectus of southern African Pteridophyta. Southern African Botanical Diversity Network Report No. 13: 1-223. SABONET, Pretoria.
• SCHELPE, E.A.C.L.E. & ANTHONY, N.C. 1986. Pteridophyta. In O.A. Leistner, Flora of southern Africa. Botanical Research Institute, Pretoria.
  
  

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  Author Ronell R. Klopper National Herbarium, Pretoria February 2004