Osmunda regalis – July 7th 2025 – Royal Fern
Osmunda regalis, late June, showing mature fertile fronds. Image: Chris Jeffree.
The Royal Fern Osmunda regalis has no association with royalty; it earns the name ‘royal’ by being the largest and most majestic of all European ferns. In his 1597 Herbal, Gerard gives us the several 16th Century names of this fern: it was never called Royal Fern. Of all the early names, the one I like best is Osmund the Waterman. ‘Osmund’ refers to the Saxon name for Thor, the god of war and creator of thunder and lightning. ‘Waterman’ refers to the fern’s liking for fens, ponds and wet woods. A native plant, it was widely collected from the wild and planted in the gardens of large estates during the ‘fern craze’ of Queen Victoria’s reign.
This specimen may be seen in the Dean Cemetery, Edinburgh, on the grave of James Jamieson MD, 1790-1867. The species is said to be ‘long-lived’, but just how long we do not know. Image: William Donachie.
It is still seen in the large gardens of stately homes, often alongside other imposing specimens such as Gunnera manicata. But it is quite common in the wild, with its British and Irish distribution being skewed to the west, where the rainfall is highest; in the wettest parts of Ireland it may be found growing in farmers’ fields.
Mid-May: garden specimen with fronds unfurling, like a fiddle-head. Image: Chris Jeffree.
The plant forms a pronounced tuft from which the leaves sprout in the spring. It produces separate vegetative and spore-bearing (fertile) leaves. The pale green vegetative leaves (‘fronds’) are large (20-60 cm). The fertile leaves rise above the others, and they have leaflets that lack any green blade. Instead, they have clusters of rusty-brown spore cases. The spores are wind-dispersed and on wet ground they germinate to form the sexual phase of the life cycle – the tiny heart-shaped prothallus (the ‘gametophyte’). As with all ferns, the prothallus has male and female sexual organs. Mobile sperm cells are shed by the male; they swim in water-films, then fertilise the female egg cells from which baby ferns arise (the ‘sporophyte’). A fine illustration of the fern life cycle can be found here.
Osmunda regalis detail of fertile frond showing sporangia before ripening. Image: Chris Jeffree.
Osmunda regalis has been widely used by researchers to study plant chromosomes, following the pioneering work by Irene Manton at Manchester then Leeds University1. She published a scholarly article in 1939, showing the size, shape and number of chromosomes, and their behaviour during cell division. Other researchers since have used Osmunda regalis to examine the influence of X-rays and ionising radiation on plant tissues. Remarkable recent research published in the prestigious journal Science has shown that these chromosomes can be seen even in fossil material (Bomfleur et al. 2014).
Back-lit vegetative fronds of Osmunda regalis. Note the dichotomously-branched veins shown best in the right-hand panel. Image: Chris Jeffree.
Benjamin Bomfleur and colleagues of the Swedish Museum of Natural History were able to measure the size of the nuclei revealed in fossils from Jurassic deposits in Sweden. They measured and counted the chromosomes. These authors went further than most of us might venture, showing that the measurements of the fossil nuclei matched those of an existing member of the Family, and therefore claimed that this group of plants had remained unchanged (‘genomic stasis’) over long periods of geologic time (180 million years).
The British and Irish distribution of Osmunda regalis in the wild from BSBI/Maps, showing a western skew, roughly following rainfall patterns. The species is native to much of Europe and some of Africa, and introduced to North America, South America and Australasia.
Others challenged Bomfleur’s interpretation. A group led by Harald Schneider of the Natural History Museum in London, and including co-workers from the Chinese Academy of Sciences and the Royal Botanic Garden at Kew, published their challenge in the New Phytologist. They had measured the nuclear size (by proxy, genome size) of 16 species from the Osmunda Family, and showed considerable variation. From their data they constructed an evolutionary tree and thus refuted the ‘hypothesis of genomic stasis’. Two years later, Bomfleur produced a quite different report, in which he and his co-workers constructed their own evolutionary tree based mostly on morphological characteristics.
The journal Science (which published Bomfleur’s first paper) and its British equivalent Nature are among the most highly cited of all scientific journals. However, they are sometimes criticised for a tendency to favour ‘eye-catching’ discoveries at the expense of rigour. On the other hand (and in defence of Bomfleur) the process of scientific advancement is speeded up when someone poses a ‘bold hypothesis’ for scrutiny and testing by others2.
Osmunda regalis has been utilised for centuries as a medicinal plant. Here’s what Gerard said in his Herbal of 1597:
Today, this plant retains medicinal interest; it is an important subject in the quest for natural remedies for cancer. Andrea Carpinteyro Diaz et al. (2024) found 17 compounds in the above-ground parts, including six that were new to science. She writes that Osmunda regalis is “a unique species that represents one of the last intact survivors of a Jurassic ecosystem”.
Notes
1Manton was Professor of Botany at Leeds University from 1946 until 1969; she taught Mary Gibby while Gibby was an undergraduate there (many readers will have known Mary Gibby, a leading pteridologist and cytologist based at the Royal Botanic Garden Edinburgh; Mary’s obituary is here).
2 The role of the ‘bold hypothesis’ in the progress of science was central to Karl Popper’s philosophy, described in his 1934 book The logic of scientific discovery.
References consulted
Bomfleur B et al. (2014) Fossilized nuclei and chromosomes reveal 180 million years of genomic stasis in royal ferns. Science 343: 1376-1377.
Bomfleur B, Grimm GW, McLoughlin S. (2017). The fossil Osmundales (Royal Ferns)—a phylogenetic network analysis, revised taxonomy, and evolutionary classification of anatomically preserved trunks and rhizomes. PeerJ 5:e3433 https://doi.org/10.7717/peerj.3433
Carpinteyro Diaz AE, Herfindal L, Holmelid B, Brede C, Andersen HL, Vedeler A, Fossen,T. (2024). Cytotoxic Natural Products from the Jurassic Relict Osmunda regalis L. (Molecules 29, 4247. https://doi.org/10.3390/molecules29174247
Clark J, Hidalgo O, Pellicer J, Liu H, Marquardt J, Robert Y, Christenhusz M, Zhang S, Gibby M, Leitch IJ, Schneider H. (2016) Genome evolution of ferns: evidence for relative stasis of genome size across the fern phylogeny. New Phytologist. 210(3):1072-82.
Landi M & Angiolini C (2011). Population structure of Osmunda regalis in relation to environment and vegetation: an example in the Mediterranean area. Folia Geobotanica, 46, 49-68.
Lehnert M, Monjau T, & Rosche,C. (2024). Synopsis of Osmunda (royal ferns; Osmundaceae): towards reconciliation of genetic and biogeographic patterns with morphologic variation. Botanical Journal of the Linnean Society, 205(4), 341-364.
Manton I. (1939) Evidence on spiral structure and chromosome pairing in Osmunda regalis L. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 230.568: 179-215.
Schneider H, Liu H, Clark J, Hidalgo O, Pellicer J, Zhang S, Kelly L, Fay MF, and Leitch IJ. (2015) Are the genomes of royal ferns really frozen in time? Evidence for coinciding genome stability and limited evolvability in the royal ferns. New Phytologist 207: 10-13.
Svanberg I (2012). Folk knowledge of an individual plant specimen: the case of the royal fern (Osmunda regalis L.) in Virestad Parish, Småland, Sweden. Ethnobiology Letters 3: 63-67.
©John Grace
