Plant 190

Osmunda regalis L. (Osmundaceae)


Royal fern

Osmunda regalis is a robust, deciduous fern native to Europe, Africa and Asia, that grows in woodland bogs and on the banks of streams. It forms large clumps of green, sterile, bipinnate fronds, together with fertile fronds that are covered with rusty-brown, spore-producing structures. In the autumn, the fronds turn an attractive red-brown.

The royal fern was growing in the Oxford Botanic Garden as early as 1648 but it is also native in Oxfordshire. It is easy to grow on most shady, acidic sites. However, it will also grow in full sun, if given plenty of moisture, and will tolerate alkaline soils, if they are enriched with fibrous compost.

The name Osmunda probably derives from Osmunder, a Saxon name for the weather god Thor. 'Royal fern', and the species epithet, are probably references to the plant's height; at up to 2.5 metres tall, it is one of the largest European ferns. Another common name for this fern is 'flowering fern', because of the appearance of the fertile fronds. Of course, as a fern, Osmunda regalis does not produce true flowers.

The genus Osmunda is thought to have evolved in the southern, ancient supercontinent of Gondwanaland. An early Jurassic (c. 180 million years ago), permineralised fossil rhizome (underground stem) of an Osmunda-like fern with excellent preservation of cell structure, was discovered in southern Sweden. Analysis of such well-preserved, fossilised remains suggests that neither genome duplication nor notable amounts of gene loss have occurred in the genetic architecture of the royal ferns since the early Jurassic. Consequently, the royal ferns have been elevated to an elite group of organisms described as 'living fossils'.

According to Slavic mythology, the fertile fronds of the royal fern ('Perun's flowers') have assorted magical powers, such as giving collectors the abilities to defeat demons and understand the 'language of trees'. But to acquire the royal fern, collectors must stand inside a circle drawn around the plant and withstand demonic taunts!

The young, unrolling fronds of ferns are often known as fiddleheads because of their similarities to the scroll of a violin. Worldwide, fiddleheads of many different fern species are consumed as food. Despite the belief that roasting destroys the cocktail of carcinogenic chemicals produced by many ferns, more research evidence is needed to show that such processing has the desired effect. Unlike fiddleheads of bracken (Pteridium aquilinum), those of royal ferns are thought to lack carcinogenic chemicals.

Further reading

Bomfleur B et al. (2014) Fossilized nuclei and chromosomes reveal 180 million years of genomic stasis in royal ferns. Science 343: 1376-1377.

Metzgar JS et al. (2008) The paraphyly of Osmunda is confirmed by phylogenetic analyses of seven plastid loci. Systematic Botany 33: 31-36.

Alison Quantrell