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Frustrating Ferns at Hareshaw Linn

I must confess that although I have been botanising for some time now, ferns have proven a difficult group to master. Indeed, master is probably the wrong word as despite countless trips in search of the species found across North East England, I am still but a novice. Or perhaps an improver!

Despite the difficulties associated with telling many of them apart, August is a great month to look closer at ferns and last week, I decided it was high time I bit the bullet and factored them into the programme of ‘Botanists Year’ trips I am currently leading for the Natural History Society. Knowing the perfect place, with 10 botanists in toe, we decided on a visit to the pteridologist’s paradise that is Hareshaw Linn in Northumberland.

Starting out, a variety of common and widespread ferns were easy to find as we made our way into the wooded valley. Broad Buckler-fern (Dryopteris dilatata), Bracken (Pteridium aquilinum) and Male-fern (Dryopteris filix-mas) came first, followed by the distinctive Hard-fern (Blechnum spicant) and later, some rather nice stands of Polypody (Polypodium vulgare). Upon scrutiny when I returned home, these were confirmed to the be common sort.

In the initial stages of our walk at Hareshaw Linn, several other interesting plants were noted too including Wood Melick (Melica uniflora), Giant Fescue (Schedonorus giganteus) and a sizeable patch of Good-king-henry (Blitum bonus-henricus) but ferns soon rose to the fore once more with new additions in Lady-fern (Athyrium filix-femina), with it’s lovely j-shaped sori, and the first of the day’s scaly male-ferns. After a closer look, this was revealed to be Golden-scaled Male-fern (Dryopteris affinis) on account of the rounded, toothed lower pinnule.

In my experience, most of the scaly male-ferns I check near Newcastle turn out to be Borrer’s Male-fern (Dryopteris borreri) but this did not appear to be the case at Hareshaw. Indeed, checking dozens of ferns along the initial leg of our walk, almost all proved to be affinis. We did, however, find a nice example of Borrer’s Male-fern a little further into the Linn, spending some time ogling its distinctive, square pinnules.

This aside, other new ferns included Soft Shield-fern (Polystichum setiferum), likely a new colonist at this site, and Hard Shield-fern (Polystichum aculeatum) which provided a nice opportunity for comparison. Other notable plants included Wood Horsetail (Equisetum sylvaticum) and Marsh Hawk’s-beard (Crepis paludosa).

The first true highlights came after crossing a small bridge in a deeper part of the Linn where we encountered an entirely new species for me in Beech Fern (Phegopteris connectilis). A rather rare species in our area, this fern is much more numerous in parts of Scotland, Cumbria and Wales were it favours woodlands dominated by Oak. It proved to be quite the lovely little plant.

Pausing for lunch about midway into the wood, we were pleased to stumble across a bankside strewn with Oak Fern (Gymnocarpium dryopteris) – a species I see very infrequently in the North East. This proved ample compensation for failing to find even a single example of Lemon-scented Fern (Oreopteris limbosperma) which I know from past walks inhabits the site also. Keen to add a few more species to our swelling tally, from here it was a straight hike to the site’s famed waterfall where a few more species awaited.

Arriving at the waterfall, we were pleased to note several examples of Hart’s-tongue (Asplenium scolopendrium), a typically common fern that had proved conspicuously absent thus far during our trip. The real excitement here was to be found in the walls of the ravine however, where, alongside some nice examples of Brittle Bladder-fern (Cystopteris fragilis) the group found many examples of Lobed Maidenhair Spleenwort (Asplenium trichomanes subsp. pachyrachis) – this being the only place you can see this lovely little fern in all of Northumberland. The subspecies of Maidenhair Spleenwort differs from that we see in garden walls in having scalloped margins to the leaflets and grows mainly on limestone outcrops, typically where conditions are very humid.

Interestingly, I had also expected to find Green Spleenwort (Asplenium viride) on this outcrop also, having noted it on trips in 2020 and 2022. Hopefully it is still kicking about there somewhere…

More Beech Fern (*Phegopteris connectilis*)

I make that 15 fern species in just a few hours – not bad going at all. In reality, the total was 18 including Wall-rue (Asplenium ruta-muraria), Maidenhair Spleenwort (Asplenium trichomanes subsp. quadrivalens) and Black Spleenwort (Asplenium adiantum-nigrum) observed as we departed from Newcastle. All in all, the trip was a success and I would strongly recommend that anyone with a penchant for ferns pay Hareshaw Linn a visit. You will not leave disappointed.

A Winter Walk at Hareshaw Linn

A short account of a frosty trip to Hareshaw Linn in Northumberland last weekend

Hareshaw Linn, a designated SSSI near Bellingham in Northumberland, is a truly lovely spot. One which I have visited previously in summer (writing about it here) but never during the colder months. Given the site’s reputation as a botanical hotspot perhaps that is little wonder – most plants tend to vanish in winter – but keen to get out and about in the winter air, we thought we would give it a go anyway. We certainly weren’t disappointed.

Ferns are a real specialty of Hareshaw Linn with the wooded valley and shady slopes here playing host to myriad rare and unusual species. While many of the ground-dwelling species had been flattened by recent frosts, during our walk, we noted several species including Lady-fern (Athyrium filix-femina), Male-fern (Dryopteris filix-mas) and Hard-fern (Blechnum spicant). The scaly ferns had taken a battering but it was still possible to discern Golden-scaled Male-fern (Dryopteris affinis) and its cousin, Borrer’s Scaly Male-fern (Dryopteris borreri). Hard Shield-fern (Polystichum aculeatum) with its rigid fronds also proved numerous – a welcome change to other sites I have visited recently.

Brittle Bladder-fern (*Cystopteris fragilis*)

Ferns growing higher up on rocks and trees seemed to have fared better than their relatives on the floor. On tree trunks strewn throughout the gorge, we noted both Common Polypody (Polypodium vulgare) and Intermediate Polypody (Polypodium interjectum), while boulders held Brittle Bladder-fern (Cystopteris fragilis) too. Of course, the area around the waterfall proved most productive with both local specialties observed. Lobed Maidenhair Spleenwort (Asplenium trichomanes subsp. pachyrachis) can be seen in good numbers here at its only Northumberland site. Green Spleenwort (Asplenium viride) was harder to come by but still present.

Lobed Maidenhair Spleenwort (*Asplenium trichomanes subsp. pachyrachis*)

Of course, ferns are not the only thing to appreciate about Hareshaw Linn. The site is rather beautiful in any season but now, in the depths of winter, looks remarkable clad in snow and ice. Given the sub-zero temperatures, the famed waterfall here had partially frozen making for an impressive sight. Better still was the presence of ice pancakes on the burn itself. Believed to form when foam floating on the water’s surface begins to freeze, this was the first time either of us had seen these. An impressive sight!

While everything looked more than a tad wintery at the Linn, signs of spring could also be seen and heard. The leaves of typical spring flowers such as Wood Anemone (Anemone nemorosa) had begun to appear and in the wood, various birds had begun singing. It was nice to catch the drumming of Great Spotted Woodpecker (Dendrocopos major) in particular.

Fern of the Week: Lobed Maidenhair Spleenwort

For our first plant profile, we’ll cover an unobtrusive yet beautiful little fern found in only a select few corners of North East England: Lobed Maidenhair Spleenwort.

This is an extremely rare plant that thanks to an unexpected trip to Hareshaw Linn in Northumberland, I recently had the chance to see for the first time.

Lobed Maidenhair Spleenwort

Asplenium trichomanes subsp. pachyrachis

Many of us are familiar with with Maidenhair Spleenwort (Asplenium trichomanes), the delicate, trailing fern adorning garden walls and other structures throughout our towns and cities. What you may not know, however, is that the UK is home to several subspecies of this lovely little fern, one of which is the Lobed Maidenhair Spleenwort (Asplenium trichomanes subsp. pachyrachis).

This unassuming fern grows on calcareous rocks such as limestone in shaded, humid settings. Often under rock overhangs, on steep valley sides or beside waterfalls, such as at Hareshaw Linn. Unlike it’s more familiar cousins, it is seldom found on mortared walls and is unlikely to crop up in towns.

A genuinely rare subspecies in the UK, Lobed Maidenhair Spleenwort is found at only a scattering of sites. A notable concentration can be found in south Wales, with a further cluster of records near Chester. Elsewhere, it is found sporadically in small populations at isolated sites.

This fern is widespread in Southern Europe, particularly in Spain, France and Italy, so may well be under-recorded in the UK.

The specific epithet trichomanes refers to a Greek word for fern

Lobed Maidenhair Spleenwort, spotted at Hareshaw Linn in Northumberland

Identification

Lobed Maidenhair Spleenwort is a small, tufted plant that often appears to grow flat against the surface of rock. Its narrow, green fronds are usually 5-30mm long and contain at their centre a dark, glossy mid-rib – a useful feature for seperating this group from Green Spleenwort (Asplenium viride). The pinnae or leaflets usually number in at 20-30 pairs and are arranged oppositely along the frond. All of this, however, appeals to other Maidenhair Spleenworts too, so what sets this subspecies apart?

The main difference between Lobed Maidenhair Spleenwort and other subspecies is the margin of pinnae. As its name suggests, those of this fern are distinctly lobed, almost scalloped. In contrast, those of other subspecies may be asymmetrical or rectangular but only slightly toothed. It may only be an anecdotal observation, but I think the lobes give the leaflets of this fern an arrow-like shape…

Given it’s similarities to other Maidenhair Spleenworts, it is little wonder this fern is poorly recorded. Sure, it may be rare, but it must be present unnoticed at further sites. Will you find it?

Distribution

In the North East, Lobed Maidenhair Spleenwort is restricted to just a few locations: one in South Northumberland (VC67) and three in County Durham (VC66).

In Northumberland, the most notable colony is found at Hareshaw Linn SSSI, where the species thrives on the humid rock faces surrounding the site’s waterfall. In County Durham, it has been recorded at two sites near Barnard Castle and on crags along the River Tees near Bowlees.

A festival of ferns at Hareshaw Linn

An account of a fantastic day spent exploring fern identification at the glorious Hareshaw Linn.

Ferns have always scared me a little if I am honest. Sure, I can identify the easier ones but by large, I often ignore them on my travels in favour of less intimidating flowers. That said, I have been keen to improve my fern identification skills for a while now and on Friday set out with a friend to one of the most fern-rich sites in Northern England.

Hareshaw Linn is SSSI designated for its rare ferns and bryophytes. A scenic river gorge sporting ancient woodland and a rather beautiful waterfall, it is a site I had always wanted to visit but had not yet had the chance. Until now. Expectations already high, I am pleased to say I was not disappointed with fourteen fern species observed during our stay, including several new for me.

Starting out

Having given only an obligatory glance to the Male Fern (Dryopteris filix-mas) during our walk in, it wasn’t long until the first of the day’s more interesting ferns was discovered. The pictures below show Lady-fern (Athyrium filix-femina) found growing beside the path through the gorge. A lovely, feathery species with distinctive crescent-shaped sori, the best way to identify them is, of course, to turn them over.

Next up, a new species for me and further into the gorge, it was great to finally stumble across Lemon-scented Fern (Oreopteris limbosperma). Quite a nice one to identify, the best way to tell it apart from the pack is that the pinnae decrease in size as they go down the stem. It also gives off a pleasant citrus smell when crushed.

Hardly worthy of a mention but two more abundant ferns were added here too: Bracken (Pteridium aquilinum) and Broad Buckler-fern (Dryopteris dilatata).

Feeling brave, further into the walk, we decided to take a quick look at some of the other Dryopteris on site. I think the fern pictured below is a Golden-scaly Male Fern (Dryopteris affinis) having ruled out the Narrow-scaly Male Fern (Dryopteris cambrensis) based on the length of the lowest pair of pinnules. It also didn’t seem to fit Borrer’s Scaly Male Fern (Dryopteris borreri) either but I’d be happy to be corrected!

Golden-scaled Male Fern (*Dryopteris affinis*)

Moving on, new ferns soon started to come thick and fast. First came the first of many Hard Shield Ferns (Polystichum aculeatum) spotted during the trip and secondly, lots of Hard Fern (Blechnum spicant). Feeling empowered by the earlier male fern, we also chose to take a closer look at the Polypodys growing alongside the river. With pointed tips and fronds which gradually taper towards the top and bottom, I think these were Intermediate Polypody (Polypodium interjectum).

Hard Shield Fern (*Polystichum aculeatum*)

Nine species and counting

Drawing closer to the waterfall, a quick detour from the track revealed another new species for the day: Oak Fern (Gymnocarpium dryopteris). With fronds split roughly into three triangles, this is another nice one to identify and another new species for me.

Reaching the waterfall, it was difficult not to be taken aback by the visible storm damage. The plunge pool beneath the waterfall was littered with the corpses of felled trees, likely brought down during Storm Arwen. I wouldn’t have liked to be here that night…

The plunge pool beneath Hareshaw’s waterfall

Back to the ferns, and Hareshaw Linn is the only North East site for the rare Lobed Maidenhair Spleenwort (Asplenium trichomanes subsp. pachyrachis). A nationally scarce subspecies of Maidenhair Spleenwort, the difference between them comes from the lobed, crinkley-looking pinnae. We saw many plants during our stay, all concentrated around the waterfall where they grow within cracks in the bedrock.

Here too, the steep cliffs of the gorge and fallen rocks beneath them held a number of other ferns. Some, like Hart’s-tongue (Asplenium scolopendrium) were somewhat common, though others much less so. Green Spleenwort (Asplenium viride) is a rare species locally and took some finding among the much more numerous Maidenhair Spleenwort.

Slightly more conspicuous, Brittle Bladder-fern (Cystopteris fragilis) could be seen in abundance too. The latter species concluded the day’s tally at a very respectable 14 fern species.

Other wildlife

While ferns were the purpose of the day’s trip, plenty of other wildlife was seen at Hareshaw Linn. The plantlife was particularly interesting with sightings of several species I see infrequently in the North East. Among these, Wood Horsetail (Equisetum sylvaticum), Wood Melick (Melica uniflora) and Marsh Hawk’s-beard (Crepis paludosa). Of course, several Giant Bellflowers (Campanula latifolia) were also a highlight.

The combination of beaming sun and rain showers did not prove overly encouraging to insects. However, we did see a few goodies including new hoverflies for me in Epistrophe grossulariae and Leucozona laternaria. Returning to the car park, the bee below was also spotted foraging on a Solidago sp. Thanks to Chris, this was revealed to be Grey-banded Mining Bee (Andrena denticulata), an incredibly rare species in our region.

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Lobed Maidenhair Spleenwort

Identification

Distribution

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Starting out

Nine species and counting

Other wildlife

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