This weeks species is the first plant to have made it species of the week, so as you’d expect, it’s interesting, rare and obscure! The Tunbridge Filmy-fern (Hymenophyllum tunbrigense)!
This species, for me, was the highlight of a recent field trip to Kennall Vale, especially as I never knew it was at the site! Nearly all of the 1st year bioscience students (almost 200 people) were queueing up, wondering what would be so special about the much-discussed Tunbridge Filmy-fern. Most people seemed oddly underwhelmed, but I could barely contain my excitement! I understand of course that to someone with no interest in ferns, this inconspicuous little species looks like a slightly ruffled patch of moss, but I think it’s truly beautiful. Here I am, with the fern!
The individual fronds of the Tunbridge Filmy-fern are only a few centimetres in length, and are only a very few cells thick. This gives the fern a semi-transparent appearance and film-like texture, hence the ‘filmy-fern’ part of its name. It also gives the Tunbridge Filmy-fern an appearance quite unlike any other British fern species (except for Wilson’s Filmy-fern). This fern can live for many years, and can undergo periods of drought by allowing itself to dry out almost completely.
Although the Tunbridge Filmy-fern is globally very widespread, it is rare in the UK, being confined to the extreme South-west of England, and the West of Wales and Scotland. It is also found in a few sites in South-east England (near to Tunbridge Wells), where it is declining due to loss of woodland habitat, and shading by introduced Rhododendrons. It is not only a rare species, but can also be very hard to find, as it may only grow on a few rocks in a particular area of a seemingly ideal habitat. I’ll use that as an excuse for not finding it myself on previous trips to Kennall Vale!
Unlike most of my other species of the weeks, the Tunbridge Filmy-fern is well recorded, so its distribution map probably reflects its true range. It is usually found on mossy rocks in damp, shaded, wooded river valleys and ravines. I hope that one day, all other groups of British wildlife will be as well recorded as the plants! Here is the map:
I must apologise for the blog being a day late. This time, blame the Hudsonian Whimbrel. (Blog on recent rare birds coming up midweek!).