I thought I would try identifying a few ferns before the season comes to an end. I am testing out The Fern Guide by James Merryweather which I bought a couple of months ago but haven’t got around to using. The book is one of the Field Studies Council AIDGAP publications that aims to help beginners come to grips with difficult groups of plants and animals.
The introduction to the guide is very useful in describing the scope of the book and providing tips for field identification. The book itself is a key, starting with Azolla and Pilularia through Clubmoss, Quillwort, Horsetail families to the Ferns. Each page consists of either/or questions and are illustrated with line drawings and a small distribution map of the British Isles.
I am lucky to live in a part of the country that is rich in ferns and started on the hillside above Dare Valley Country Park, near Aberdare. The first fern was this one growing below a rock outcrop.
The Key for the ferns starts on page 40 and depends on accurately determining the degree of division of the frond into pinnate, bi-pinnate, tri-pinnate etc. I decided that this plant was pinnate which put it into Key F. This was because the pinnae seemed to be deeply lobed almost to the midrib, rather than having distinct pinnules. However this proved to be the wrong choice and the plant would not key out.
When I tried to key out the fern assuming it had bi-pinnate fronds it did eventually key out but the process was quite tortuous as it involved eliminating fairly unusual plants such as Jersey Fern Anogramma leptophylla and Killarney Bristle Fern Trichomanes speciosum. I think this is quite a problem for a guide that is aimed at beginners.
The plant keyed out as Lemon Scented Fern Oreopteris limbosperma. Ironically (given the degree of technical language) Poland and Clement(2009) seems to offer a more straightforward key. Here the frond is described as 1-pinnate with pinnatisect pinnae (p.15). The greatest difficulty is identifying the hairs on the underside of the leaf which takes the key to section BD (p. 20). After this its fairly straightforward identifying the tufted habit and the numerous yellow glands.
The next fern growing just a few feet away was this Hard Fern Blechnum spicant.
Straight away there is the same problem of deciding whether it is 1-pinnate as defined by Streeter (2009) Stace (1997) and Merryweather (2007) or pinnatisect (Poland and Clement 2009). I would say my specimen was 1-pinnate and Merryweather works quite quickly but again perhaps there was no need to go via the much rarer Forked Spleenwort and Holly Fern. The identification is sealed at this point by the illustration but the description of it growing on peaty soils in a rosette form is less useful. (In this case the fern is growing on rocks which could lead us on wrongly to Polypody or Spleenwort at this point.)
The next fern was growing just below the rare and unassuming Sorbus porrigentiformis.
The kidney shaped indusia diagnose this as one of the Buckler Ferns (Dryopteris) and Merryweather offers us a choice of 5 male ferns with these lanceolate pinnae (p. 76). The dark junction of the pinnae stalk and rachis quickly takes us to the Dryopteris affinis group. Merryweather then goes on to describe the sub-species affinis, borreri and cambrensis, but I don’t think I would like to commit to any one of these.
So at this point I more or less gave up on Merryweather, because although aimed at the beginner it also provided too many options such as the D affinis group that could not really be determined. I really like the feel of the book and the colour photographs at the back are excellent. The line drawings are generally good but often lack enough detail. Most of all though the keying process was too slow and the definition of terms like pinnate unclear.