Acrostichum ilvense L. (basionym)
Woodsia ilvensis, commonly known as oblong woodsia, is a fern found in North America and northern Eurasia. Also known as rusty woodsia or rusty cliff fern, it is typically found on sunny, exposed cliffs and rocky slopes and on thin, dry, acidic soils.
Its distribution is circumpolar and is most abundant in Scandinavia, the Ural and Altai mountains and the eastern United States. It is also found in Japan, Alaska, Canada, coastal Greenland and various European locations including the Alps.
It is considered "Threatened" or "Endangered" in the states of Illinois, Iowa, and Maryland and "Presumed Extirpated" in Ohio. Also found in West Virginia and North Carolina, it is the most common Woodsia species in the US.
Its UK distribution is confined to Angus and the Moffat Hills in Scotland, north Wales and Teesdale and the Lake District in England. There are fewer than 90 wild clumps in the whole of the UK, where it is on the edge of its natural range and is considered to be "Endangered".
Discovery and identification
The plant was first identified as a separate species from specimens collected in Scotland in Bolton's 1785 publication Filices Britannica. Bolton distinguished between Acrostichum ilvense and Acrostichum alpina, now Woodsia ilvensis and Woodsia alpina respectively, which had previously been conflated. The genus Woodsia was established in 1810 by Robert Brown, who named it named after the English botanist Joseph Woods. "Ilvensis" is the genitive form of the Latin name for the island of Elba.
The leaves are typically 6 inches long and 1 inch wide, with stiff, erected pointed tips and cut into 12 nearly opposite stemless leaflets. The underside of the leaves are covered in white woolly fibres, which later turn rusty brown.
Victorian collectors and modern conservation
Oblong woodsia came under severe threat from Victorian fern collectors in the mid 19th century in Scotland, especially in the Moffat Hills. These hills once had the most extensive UK populations of the species but there now remain only a few small colonies whose future is under threat. This period of collecting became known as pteridomania (or "fern-fever"). The Royal Botanic Garden Edinburgh plan to use cultivated specimens and a spore bank to restore depleted wild populations.
- "Woodsia ilvensis (L.) R. Br.". PLANTS Profile. United States Department of Agriculture. Retrieved 18 June 2008.
- "Woodsia ilvensis (Linnaeus) R. Brown, Trans. Linn. Soc. London, Bot. 11: 173. 1813". Pteridophytes and Gymnosperms. Flora of North America. 2. Oxford University Press. 1993. ISBN 978-0-19-508242-5. Retrieved 18 June 2008.
- "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-02-25. Retrieved 2014-10-17.
- Tom Stuart. "Woodsia ilvensis". Hardy Fern Library. Retrieved 18 June 2008.
- Earl J. S. Rook (26 February 2004). "Woodsia ilvensis". Retrieved 19 June 2008.
- Phillip Lusby & Jenny Wright (2002). Scottish Wild Plants: Their History, Ecology and Conservation (2nd ed.). Edinburgh: Mercat. pp. 107–109. ISBN 1-84183-011-9.
- "From coast to summit - two Woodsia ferns". Royal Botanic Garden Edinburgh. Retrieved 5 June 2008.
- Boughton Cobb (1975). A Handbook of Ferns and their Related Families in the North American Continent Based on Visual Identification. Peterson Field Guides. Houghton Mifflin Harcourt. p. 146. ISBN 0-395-97512-3.
- Media related to Woodsia ilvensis at Wikimedia Commons