Fern identification in Wales

Cwm Idwal
Image: F. O'Neill

Fiona tells us about a fern identification course she attended recently:

"In mid-July I travelled from Cork, with my naturalist friend, to North Wales to attend a fern (and allies) identification course at the Field Studies Council (FSC) centre in Rhyd-y-creuau, near Betws-y-coed village. We arrived a few days before the course started to explore a little of North Wales, and really, you should go there, it’s fantastic, with walks galore and stunning scenery.

"On Friday evening, the course participants met at Rhyd-y-creuau for dinner followed by an overview of the next three days. 13 attended, with six taking the course for credits towards an MSc, and the remaining seven having a general interest in ferns. Our tutors were Chris and Hazel Metherell, Chris is the current BSBI President and Hazel is an artist and botanist with a particular interest in ferns.

Cryptogramma crispa
Image: F. O'Neill

"After dinner we kicked off with a video called Ferns: The Secret Life, looking at their unique sexual reproduction processes. The recommended text for the course was The Fern Guide by James Merryweather & Michael Hill (2007, originally published in 1995), valuable for its illustrations and descriptions. And during the evening, Chris and Hazel outlined the method they use to ID ferns—more of that in Fern ID tips at the end.

"On Saturday morning we crammed into the mini-bus, driven by Chris, and headed to a national nature reserve, Cwm Idwal, a spectacular glacial corrie in the Glyderau mountain range. There’s a popular walk around the lake, Llyn Idwal, and other paths branching off it that take you higher. The day turned misty and drizzly, which didn’t affect the ferns in the slightest just our views of the cwm and our ability to write on damp notepaper—the scene below was one I fortunately prepared earlier in the week on a recce.

Lycopodiella inundata
Image: F. O'Neill

"The first two ferns Chris stopped at and used to go through his identification method were the relatively common Dryopteris dilatata (Broad buckler fern) and Asplenium trichomanes (Maidenhair spleenwort), the first is tripinnate and the second once-pinnate. Next, we encountered two upland ferns, Oreopteris limbosperma (Lemon-scented or Mountain fern) and the bushy Cryptogramma crispa (Parsley fern), the latter is plentiful here, but a rarity in Ireland.

"As we made our way higher, we paused often to look closely at ferns, clubmosses, and occasionally other plants found in alpine habitats, including Saxifraga nivalis (Alpine saxifrage), existing on just one remaining rock, an indication that alpine plants are really struggling here.

"Cwm Idwal is home to four clubmosses and we were fortunate to see all of them: Lycopodium clavatum (Stag’s horn clubmoss), Huperzia selago (Fir clubmoss), Diphasiastrum alpinum (Alpine clubmoss), and Selaginella selaginoides (Lesser clubmoss).

Fun times on Saturday night
Image: F. O'Neill

"Among other unfamiliar ferns I saw were Cystopteris fragilis (Brittle bladder fern) and Phegopteris connectilis (Beech fern), both rare in the southern half of Ireland. C. fragilis can resemble young ferns of other species, therefore care needs to be taken to confirm the ID. P. connectilis has a couple of unique attributes that are useful in identification, the pinnae nearest the stem are entirely attached to the stem, and the lowest pinnae point out and downwards.

"Throughout the day we listened, and took notes, as Chris and Hazel clearly and patiently imparted their knowledge; Hazel often went ahead to check out the next species and waited for us to catch up.

"

Asplenium septentrionale
Image: F. O'Neill

On the way back from Cwm Idwal, we pulled in to the side of the road and hopped over a stile with Hazel to locate the fifth clubmoss of the day, Lycopodiella inundata (Marsh clubmoss) by a farm track.

"That evening, we got a taste of a lively Saturday night outing for botanists, a trip to a lead mine spoil heap in Gwydyr Forest Park, looking at Asplenium septentrionale (Forked spleenwort). It likes to be alone and is into heavy metals.

"On this marathon day we looked at 20 ferns and five clubmosses. 

"On Day 3, we headed to Anglesea, where we dashed around to seven different sites on a botanical treasure hunt for ferns and horsetails. Down country lanes for the polypodies, Polystichum aculeatum (Hard shield fern), and Asplenium adiantum-nigrum (Black spleenwort). To the coast for some sea air and Asplenium marinum (Sea spleenwort). And wading through bracken and briars to Thelypteris palustris (Marsh fern) and Dryopteris carthusiana (Narrow buckler fern).

En route to Dryopteris carthusiana
Image: F. O'Neill

"In the morning Chris introduced us to horsetails, and over the day we identified Equisetum arvense (Field horsetail), the most common species, Equisetum palustre (Marsh horsetail), Equisetum fluviatile (Water horsetail), and finally Equisetum x meridionale, one clump of which was near an RSPB reserve and has possibly been there for decades.

"Chris's tip for E. arvense and E. palustre: remember the acronym ALPS (Arvense: Long, Palustre: Short). This means that when you compare the length of the first junction of a side branch to the length of the sheath, it’s E. arvense if it’s longer than the sheath, and E. palustre if shorter.

"Arriving at our final destination for the day, we crossed the Menai bridge to nearby Treborth Botanic Garden, to view two rarities, Polystichum lonchitis (Holly Fern) and Woodsia alpina (Alpine woodsia).

After dinner at Rhyd-y-creuau, work continued. We examined polypody spores under the microscope, and Hazel introduced plant genetics, hybrid vigour, and explained what diploid and triploid plants are. 

Blechnum spicant
Image: F. O'Neill

"Chris then spoke about the complex Dryopteris affinis group, which is likely to be split out into many microspecies within the next few years. We were very happy to just contend with these three:

Dryopteris affinis (Scaly male fern)

Dryopteris borreri (Borrer’s scaly male fern)

Dryopteris cambrensis (Narrow scaly male fern).

"On the final morning we travelled to Coed Felinrhyd, described as “Wales’ own rainforest”. The shady and humid oak woodland is home to a wealth of ferns and bryophytes, and is a Special Area of Conservation (SAC) for bats.

"The sheer number of fern species here gave us the chance to revise what we learned from the previous two days. We were given the challenge of IDing ferns in the D. affinis group, which, when you’re with the experts, actually seems possible. We found examples of all three, the very scaly D. affinis; D. borreri is a neater plant and the pinnules look as if they’ve been razored across the top; in D. cambrensis the lowest pinnule “steps up” from the next. Of course, some of these characteristics are variable.

Phegopteris connectilis in Coed Felinrhyd
Image: F. O'Neill

"A week later ferns, clubmosses, and horsetails are still on the brain. Chris and Hazel couldn’t have been more generous with their knowledge and time, we learned so much and felt very lucky to have them as our tutors.

"Some highlights for me over the weekend included the abundant clumps of Blechnum spicant (Hard fern) in Coed Felinrhyd, its distinctive fertile fronds emerging from the centre; a Saturday night out looking at the heavy metal tolerant A. septentrionale (Forked spleenwort), and finally, seeing the graceful little P. connectilis (Beech fern) for the first time on Cwm Idwal and in Coed Felinrhyd.

Addendum: Fern ID tips

"Rather than use keys to identify fern species, Chris and Hazel ask three (sometimes four) questions to arrive at the answer. The first two questions are always the same, and sometimes are all that are needed; questions three and four vary, depending on the answer to the previous two.

Indusium*. Does it have one? What is it like? For example, is it linear (Asplenium), c-shaped (Dryopteris), or j-shaped (Athyrium)?

What is the pinnateness of the plant? From 0 to 4, simple to tripinnate.

Examples of question 3 are:

What shape is the frond? For example, does it taper or stop suddenly?

What are the scales like? For example, do they have a dark central stripe?

Are the pinnae stalked? Diagnostic for Asplenium.

The fourth question is only required for a small number of ferns to reach an ID, an example is:

What colour is the rachis**?

*Indusium: Protective membrane covering the sporangia.

**Mid-rib, excluding the stipe".

Many thanks to Fiona for telling us about the fern course she attended. I'm looking forward to meeting her on Wednesday, when we'll both be at the BSBI Mayo Recording Event 2018 - any fern I see, I'll be asking Fiona to help me ID it! Watch this space ;-)