Motivated by last year’s fern forays and spurred on by my new membership of the British Pteridological Society, I have decided to try something different this year: a personal challenge to see as many of Britain’s fern species as possible in a single year. The idea being that, by seeking out our ferns, I’ll learn more about them, their habitats, and the subtleties involved in identifying them. This blog will be part #3.
Asplenium x clermoniae – 26th January
On Sunday, a trip north into rural Northumberland provided a welcome opportunity to check in on one of the rarest and most intriguing ferns in North East England: Lady Clermont’s Spleenwort Asplenium × clermontiae – a hybrid I hadn’t seen since 2023, when I published a short blog about it here.
To cut a long story short, this is an exceedingly rare hybrid between Wall-rue Asplenium ruta-muraria and Maidenhair Spleenwort Asplenium trichomanes subsp. quadrivalens. On paper, it ought to be more widespread, given the abundance of its parent species, but this is very much not the case. In fact, it is currently known from just three individual plants across the entirety of the British Isles. The Northumberland plant has been known since the early 2000s and has been visited by many pteridologists over the years.
It is a rather unruly-looking fern, showing characteristics of both parents, and so far as this year’s pteridological challenge goes, an excellent one to notch up early on.
Lady Clermont’s Spleenwort Asplenium x clermontiae
A short distance away, another unassuming wall played host to a second rare little spleenwort, though not quite so rare as the species mentioned above. Rustyback Asplenium ceterach is common in many parts of the UK but decidedly scarce in the North East and, despite an abundance of seemingly suitable habitat, remains confined to a small number of quarries and walls across the region. I do wonder whether climate plays a part. In North Northumberland, it is a Rare Plant Register species, meaning it should be reported whenever encountered.
A lover of limestone rocks and lime-rich mortar, this species is easy to identify thanks to its thick, leathery, almost once-pinnate fronds and the dense covering of rust-coloured scales on the underside. The images below show one of two plants observed during a brief pit stop at a well-known site.
Another species down…
Rustyback Asplenium ceterach
Running Total
Seeing as I rarely carry a notebook, we’ll log our running total for the year here…
Motivated by last year’s fern forays and spurred on by my new membership of the British Pteridological Society, I have decided to try something different this year: a personal challenge to see as many of Britain’s fern species as possible in a single year. The idea being that, by seeking out our ferns, I’ll learn more about them, their habitats, and the subtleties involved in identifying them. This blog will be part #2.
Woodland Ferns – 17th January
By January, our woodlands are not looking especially vibrant. Cold, wet, and muddy, they are far removed from their spring splendour, and by this point in the year, most of our ferns are looking rather jaded too.
With this in mind, yesterday saw us meandering through Jesmond Dene, keen to see what could still be picked out in the depths of January. As expected, most of the ferns looked rather gnarled by the frosts, but in sheltered spots our two most familiar woodland species could still be found.
Broad Buckler-fernDryopteris dilatata, with its broad, wedge-shaped fronds and dark-centred scales, was easily located, as was Male-fernDryopteris filix-mas with its tapering fronds and toothed pinnules. These are perhaps our most abundant native ferns both will look far better come spring.
Broad Buckler-fern Dryopteris dilatata, with its broad, wedge-shaped frondsMale-fern Dryopteris filix-mas with its tapering fronds and toothed pinnules.Toothed, tapering pinnules of Dryopteris filix-mas
Continuing our walk, it was also pleasing to see several healthy clumps of Hart’s-tongue Asplenium scolopendrium looking altogether more robust and vibrant than the straggly individuals spotted on walls during our previous outing.
A healthy example of Hart’s-tongue Asplenium scolopendrium clinging to a bank.
Another group of evergreen woodland ferns still visible at this time of year are the Polystichum species – the Shield-ferns. Our two native species are both fairly common in shady woodland settings and are easily recognised by their distinctly “mitten-shaped” pinnules. They can be told apart by a combination of features, most notably the overall shape of the frond (gradually tapering versus ending abruptly), whether the pinnules are stalked, and the angle of the lowest pair of pinnules (obtuse vs acute).
In images one and three below, we have Soft Shield-fernPolystichum setiferum: soft to the touch, with a truncate base and pinnules set at an obtuse angle. The third image shows an escaped cultivated form, noticeably more frilly in appearance – a reminder of the interesting things we humans have done to ferns. Note in both examples, the pinnules are stalked. This is also a useful factor in separating these species, as set out in the helpful crib here. A good blog on the two native species can also be found here.
Pinnules of Polystichum setiferum, soft to the touchA cultivated form of Polystichum setiferum with very frilly foliage.I did toy with the idea of this plant being the hybrid of Soft and Hard Shield-ferns but alas, I think it just P. setiferum
Close to the first Shield-fern, we also noticed a rather lovely Polypody Polypodium sp clinging to a bridge. I have learned through bitter experience how difficult it is to separate these species on visual characters alone, so having collected a small sample, I’ll be checking the spores later. Stay tuned for another post on those.
A nice Polypodium species clinging to the stonework of a bridge.
Last but not least on our morning walk through Jesmond Dene, we stopped to check in on a more unusual fern, first noted last year while recording for my upcoming Urban Flora of Newcastle. At first glance, you might notice that it looks rather similar to the Soft Shield-fern shown previously – and that’s because it is, albeit a little more exotic in nature.
This plant is, in fact, Japanese Lace FernPolystichum polyblepharon, a widely cultivated garden species that appears to have found its way into the Dene of its own accord. This young plant is growing on a steep, muddy bank where deliberate planting seems highly unlikely, and so can presumably be counted towards this year’s fern fest. As mentioned previously, non-native ferns will count provided they appear to be self-sown.
Japanese Lace Fern Polystichum polyblepharon, an oddity of Jesmond Dene
Right Back at It – 23rd January
After work on Friday, I opted for a rather rainy afternoon walk back into the Dene, this time venturing a little further to see what I could find. It was pleasing to come across another Polypodium, this time growing on a tree, though it lacked the spores needed for identification.
Polypodium species growing on a moss-covered tree in Jesmond Dene
Further along the Ouse Burn, the challenge’s next “new” fern became apparent: Hard Shield-fernPolystichum aculeatum, with its sessile, acute-angled pinnules and tapering fronds. This is one of the scarcer of the ‘common’ ferns in my part of Newcastle, so it’s always nice to see.
Young Hard Shield-fern Polystichum aculeatum clinging to a slopePinnule shape of Hard Shield-fern Polystichum aculeatumA larger specimen of Hard Shield-fern Polystichum aculeatum
In the same area that held the shield-fern, it was also pleasing to find two slightly straggly examples of the once-pinnate Hard FernBlechnum spicant. This species needs little introduction.
Hard Fern Blechnum spicant in Jesmond Dene
Slightly more perplexing are the Scaly Male-ferns Dryopteris affinis agg. These were always going to be the most difficult group to contend with during this year’s fern challenge, and no matter how much time I spend looking at them, they still manage to confuse me. Inevitably, I find myself examining a great many specimens before eventually settling on one that matches the descriptions in the various resources stuffed into my rucksack – most of which contradict one another to some degree.
The two common species involved are Borrer’s Scaly Male-fern Dryopteris borreri and Western Scaly Male-fern Dryopteris affinis subsp. affinis.
A selection of Scaly Male-ferns in Jesmond Dene
D. affinis subsp. affinis is soundly evergreen, so as a first step, I looked for a fern that still appeared reasonably fresh for mid-January. Having succeeded, it was time for a closer inspection. As far as I recall, affinis is the only one of the common Scaly Male-ferns to have an adnate lowest basiscopic pinnule (that is, lacking a stalk). It also has rather lucid veins that extend all the way to the pinnule margin, and lowest pinnules on each pinna that are roughly the same size as their neighbours, unlobed and rounded at the tip.
The fern shown below seemed to fit this description, at least in most respects. With a degree of trepidation, I’m therefore calling it Dryopteris affinis subsp. affinis.
Lowest pinnules of Western Scaly Male-fern Dryopteris affinis subsp. affinisLowest basiscopic pinnule of D. affinis
In contrast to affinis, D. borreri has stalked lowest basiscopic pinnules and lowest pinnules that are slightly longer than their neighbours. These are also toothed at the corners (in the typical form, at least) and show slightly more diffuse venation that stops short of the pinnule margins. All quite straightforward in theory.
Taking a frond from one slightly more convincing example and examining it more closely, most of these characteristics are present, particularly in the shape of the pinnules. However, I don’t yet feel that I’ve fully got to grips with the differences in venation. The plant I tentatively labelled as affinis does not appear identical to examples I have seen online. This borreri, however, shows the pale blotching often mentioned in the literature, which is reassuring.
Lowest pinnules of Dryopteris borreriPale blotching between veins that (largely) stop short of the pinnule margin
We’ll certainly have to revisit these before attempting any of the rarer ferns within the complex, but hey, practice makes perfect (or so I am told).
Running Total
Seeing as I rarely carry a notebook, we’ll log our running total for the year here…
Motivated by last year’s successful fern forays, and spurred on by my new membership of the British Pteridological Society, I have decided to try something different this year: a personal challenge to see as many of Britain’s fern species as possible in a single year. The idea being that, by seeking out our ferns, I’ll learn more about them, their habitats, and the subtleties involved in identifying them.
The premise is simple: any fern growing in a wild situation counts, as do subspecies, hybrids, and species accepted by the major authorities. I will do my utmost to document each new find here, beginning with easily accessible species and, hopefully, progressing to trickier ones further down the line.
Urban Ferns – 16th January
It seemed reasonable to kick-start this year’s pteridological challenge with something low-key and ordinary. Thus, a search for wall ferns was on the cards.
On a typical street in Newcastle, there are four or five ferns that commonly occur on walls, most of which belong to the genus Asplenium. What I find especially interesting about Asplenium is that it is a genus of polar opposites. Perhaps half a dozen species are so widespread as to seem almost mundane, while others rank among our most elusive ferns, known only from a few carefully guarded sites. When it comes to the former group, the good news is that you don’t need to travel far to find them.
Skulking along some Heaton terraces, it wasn’t long before we came across our first species: Wall-rueAsplenium ruta-muraria, growing snugly in the mortar. Around fifteen plants clung to the wall, many stunted but unmistakable on account of their small, fleshy, club-shaped fronds. It is an easy species to recognise, and one of the commonest of our ferns.
A healthy clump of Wall-rue Asplenium ruta-murariaA pitiful example of Wall-rue Asplenium ruta-muraria growing alongside Hart’s-tongue
Mixed in among them were examples of Maidenhair SpleenwortAsplenium trichomanes, its fronds borne on dark, wiry stems and clustered in tight tufts within the mortar. While easy to recognise at first glance, there is more to this little fern than meets the eye. What we collectively know as Maidenhair Spleenwort is, in fact, an aggregate of three subspecies, each occupying its own ecological niche. Two of these are rather rare; the third is incredibly common.
Distinguishing between the subspecies requires attention to detail: the shape of the pinnules, the point of insertion of the stalk, the colour of the rachis, and the angle of growth against the substrate. Truth be told, it is a fiddly, detailed, and at times frustrating affair – though it is possible to cheat. The simplest shortcut is habitat. The commonest subspecies, quadrivalens, is a calcicole: a lover of lime. In the wild, it grows on calcareous rocks, but it is equally at home in the lime-rich mortar of brick walls. The second, trichomanes, is a much rarer plant of acidic rocks, typically confined to upland areas and occasionally encountered on dry-stone walls. The third, pachyrachis, is so scarce that it barely warrants consideration here, though for completeness it favours damp limestone and is restricted to just a few corners of the British Isles. By process of elimination, our plant could only be subsp.quadrivalens – a conclusion quickly confirmed by the insertion of the stalk at the corner of each pinnule.
A sorry example of Maidenhair Spleenwort Asplenium trichomanes subsp. quadrivalensA healthier colony of Maidenhair Spleenwort Asplenium trichomanes subsp. quadrivalens on a sheltered wall
Where these two species occur, a third often appears as well, though it rarely looks healthy when growing on walls. Hart’s-tongueAsplenium scolopendrium may tolerate such habitats, but it much prefers the shade and humidity of woodland, where it typically grows on mildly alkaline soils. Perhaps our most recognisable native fern, with its glossy, lime-green, tongue-like fronds, it presents few challenges. It is also a particularly useful Asplenium for demonstration purposes. The specific epithet scolopendrium is derived from the Greek skolopendra, meaning centipede – an allusion to the arrangement of the sori on the underside of the frond in parallel lines, a key feature of this genus.
Hart’s-tongue Asplenium scolopendrium emerging from an exterior wall
Moving on to another terrace, along another street lined with delightfully neglected student front gardens, there was one more species on the day’s agenda. Another Asplenium, though one that, in my experience, is typically harder to come by: Black SpleenwortAsplenium adiantum-nigrum. Unlike the wall specialists already encountered, this species is not a strict calcicole. Instead, it favours base-enriched substrates containing modest amounts of calcium or magnesium. For this reason, it is often found on mortared walls, though it grows equally well on natural rock faces and on ruins built from basic stone. It is common in many parts of Britain, but here in the North East, it is by no means abundant.
While it took some finding, after a short while, we managed to locate one small, rather pitiful example peeking out from a crevice. It will do for now!
A stunted example of Black Spleenwort Asplenium adiantum-nigrum on a neighbor’s wall
Running Total
Seeing as I rarely carry a notebook, we’ll log our running total for the year here…
