Plant 375

Adiantum species (Pteridaceae)

Maidenhair ferns

The cosmopolitan genus Adiantum comprises more than 200 species of shade-loving, terrestrial ferns. The genus is readily recognised by its fronds which typically have wiry, highly polished, dark purple to black stalks with highly dissected blades of delicate, fan-shaped segments. The generic name, derived from a Greek word meaning ‘incapable of being wetted’, refers to water droplets that readily slide from the surfaces of the fronds.

Another distinctive feature of the genus Adiantum is that its spore-producing structures (sori) are arranged around the edge of the frond on the lower surface. The sori are covered by a flap of frond margin which bends back over them, giving the edges of frond segments in some species a gnawed appearance.

One species, Adiantum capillus-veneris, the true maidenhair fern, is native to the United Kingdom, where it is a rare species of maritime cliffs and rocks. However, Adiantum capillus-veneris is not rare globally. It has a worldwide distribution that extends from temperate to tropical regions, and forests and woodlands to the margins of water courses and rock faces. One of the earliest records of this fern is Britain was made by the second Keeper of the Ashmolean Museum Edward Lhuyd, as he explored Glamorgan, Wales, in the late 1690s.

The name capillus veneris (‘hair of Venus’) was adopted by herbalists from its use in fourth-century European Latin texts, where it appears to refer to numerous ferns with similar appearances and medicinal properties. The properties attributed to the true maidenhair fern were those of a panacea, it being used in the treatment of conditions as diverse as coughs, kidney stones and the King’s Evil (scrofula). It was even reputed to make ‘the haire of the head or beard to grow that is fallen and pilled [pulled] off’.

Adiantum species are popular plants in the horticultural trade. In the nineteenth century, natural mutants of the true maidenhair were collected from the wild in Britain, propagated and bred to produce ferns that varied in the form and colour of their fronds. Most Adiantum species are tender, making them valuable houseplants. The south and southeast Asian Adiantum caudatum is cultivated indoors for it long, arching fronds. When the frond tips touch the ground they root, producing new plants – hence one of its common names, walking maidenhair. Some species, such as the North American Adiantum pedatum, with its distinctive fan-shaped fronds, will grow outside in the United Kingdom.

Further reading

Cobb B et al. 2005. A field guide to ferns and their related families of northeastern and central North America. Houghton Mifflin Company.

Merryweather J 2020. Britain's Ferns: A field guide to the clubmosses, quillworts, horsetails and ferns of Great Britain and Ireland. WildGuides.

Page, CN 1997. Ferns of Britain and Ireland. Cambridge University Press.

Stephen Harris