I had wanted to visit a limestone pavement for what felt like many years, ever since first encountering the habitat in GCSE geography lessons – and even more so once I became interested in botany. This past Sunday, I finally had the chance when Matt agreed to drive two hours from Newcastle to Great Asby Scar.
Widely regarded as one of the finest examples of limestone pavement in England, Great Asby Scar lies on a hillside between the villages of Orton and Great Asby. Once heavily plundered by Victorian gardeners in search of decorative limestone, the site is now strongly protected as both a Site of Special Scientific Interest (SSSI) and National Nature Reserve (NNR), largely because of the remarkable wildlife supported by this rare habitat. For our visit, we opted for a short route from a convenient nearby car park, though as the route map here shows, it would be very easy to extend the walk and take in even more of the spectacular scenery.
Limestone pavements are rare and highly specialised habitats, characterised by flat, block-like slabs known as clints and deep, nutrient-rich fissures called grikes. Together, these create a remarkable mosaic of microhabitats, where shade-loving woodland plants can thrive just inches away from drought-tolerant species exposed to the full sun. Among these are a host of interesting ferns — the main reason for our visit.
Setting out from the car park, it was not long before we encountered our first species among smaller outcrops of limestone beside the ascending path. Here, Hart’s-tongue Asplenium scolopendrium grew alongside the lime-loving Maidenhair Spleenwort Asplenium trichomanes subsp. quadrivalens and Wall-rue Asplenium ruta-muraria. All are relatively common species, but it was pleasing to see them in a natural setting. Accompanying them were abundant Blue Moor-grass Sesleria caerulea and several woodland plants tucked away within the grikes, including Ramsons Allium ursinum and Dog’s-mercury Mercurialis perennis.
The thin calcareous grassland lining the path on our approach also held plenty of interest, including some lovely colonies of Early-purple Orchid Orchis mascula. This species occurs here in impressive abundance. Much less conspicuous were Knotted Pearlwort Sagina nodosa and Thyme-leaved Sandwort Arenaria serpyllifolia, though both were flowering happily among the shorter turf.
More exciting still was a duo of scarce and rather diminutive ferns spotted as we neared the gate into the reserve. First came a solitary Adder’s-tongue Ophioglossum vulgatum, followed shortly afterwards, much to my delight, by a fine example of Moonwort Botrychium lunaria, one of my favourite pteridophytes and a species I encounter only very infrequently indeed.
After this, we entered the main part of the reserve, passing a handy information panel before emerging onto an expansive area of limestone pavement. What struck us immediately was how each grike seemed to support its own distinctive assemblage of species. This diversity would have been very easy to spend an entire day peering into the crevices. Unfortunately, we did not have all day, so we quickly set about searching for some of the specialist ferns we had travelled such a long way to see.
Finding these species proved fairly straightforward, in truth, as all grow conveniently close to the path. First came several large colonies of Limestone Fern Gymnocarpium robertianum, a rather lovely species that, until now, I had only encountered in cultivation. Here, however, it seemed to be everywhere, spilling from grikes and shaded ledges in impressive abundance.
The next species, Rigid Buckler-fern Dryopteris submontana, was somewhat less abundant, though still present in respectable numbers. Highly susceptible to grazing, this rather understated fern has its British strongholds in the limestone pavements of Cumbria and Yorkshire. It can be distinguished from similar-looking species by the distinctly glaucous tone of its fronds, caused by the copious glands spread across the frond surface.
Growing alongside these were Green Spleenwort Asplenium viride, Brittle Bladder-fern Cystopteris fragilis and plenty of Western Scaly Male-fern Dryopteris affinis subsp. affinis. Had we spent more time scrutinising the male-ferns, we would almost certainly have found additional taxa among them. Plenty of Hard Shield-fern Polystichum aculeatum could also be seen, alongside the ever-present Male-fern Dryopteris filix-mas.
As things transpired, we located the vast majority of our target species rather quickly, leaving plenty of time for an enjoyable circular wander around the reserve to see what else we could find. Within the grikes, it was particularly nice to encounter Lily-of-the-Valley Convallaria majalis alongside the more familiar woodland flora. Other notable finds included Hairy Rock-cress Arabis hirsuta, Limestone Bedstraw Galium sterneri and an abundance of Mouse-ear-Hawkweed Pilosella officinarum with its cheerful lemon-yellow flowers.
We probably ought to have spent more time examining the sedges and grasses, but with temperatures creeping towards 21°C during our visit, we were beginning to feel fairly well cooked by that point.
Deciding we were getting a little too warm, after a few hours, we eventually began the walk back from the scar. Had we spent longer there, no doubt many more interesting species would have revealed themselves, but even so, we enjoyed a wonderful few hours in what is a beautiful, diverse and incredibly atmospheric landscape.
I can certainly understand why so many people extol the virtues of northern England’s limestone pavements, and I will undoubtedly be returning to explore them again in the future.