Howard M. Beck

HOWARD M. BECK

At 723 metres, Ingleborough, the second highest of the famous hill trilogy of the Yorkshire Dales, has long been recognised to be of national importance for its native flora. This botanical treasure chest is home to many nationally scarce vascular plants, such as Actaea spicata (Baneberry), Potentilla crantzii (Alpine Cinquefoil), Polygonatum odoratum (Angular Solomon’s-seal), Primula farinosa (Bird’s-eye Primrose), Epipactis atrorubens (Dark-red Helleborine), as well as actual rarities like Arenaria norvegica subsp. anglica (English Sandwort – or ‘Yorkshire Sandwort’ as we like to call it) and species of Hieracium (hawkweeds) and Alchemilla (Lady’smantles).

In recognition of this floral mosaic, the archaeology and its geodiversity, Ingleborough (situated in v.c.64 – Mid-West Yorkshire) was notified as an SSSI in

Above: Sulber, Ingleborough (v.c. 64), looking east; habitat of Viola rupestris (Teesdale Violet). Photographs by the author.

1955. Almost a decade later in 1962, the purchase by the Nature Conservancy Council of 8.9 ha of land comprising Colt Park Wood established the Ingleborough NNR. Since then land acquisitions by both the Yorkshire Wildlife Trust and English Nature (now Natural England) on the north, north-east, east and south-eastern sides of the summit plinth have over the years increased the size of the reserve to 1,024 ha. This represents one fifth of the SSSI total. Around Christmas 2019 Colin Newlands, Natural England’s senior reserve manager (now retired) on the Ingleborough reserve, drew my attention to another diminutive but nationally rare plant, Viola

rupestris (Teesdale Violet). He added, almost wistfully, that it was anyone’s guess quite how widespread the species might prove to be on the reserve, or in what numbers. It was a shortcoming, he went on, that would only be addressed were someone to undertake a comprehensive survey.

V. rupestris is a Eurasiatic species with a widetemperate distribution, extending from Sakhalin in the Russian Far East to western Europe. In Britain the species has a northern montane distribution and so far is found in just four areas of England. It is a long-lived calcicole favouring substrates with a soil pH of more than 6.0. A perennial in nature, it normally flowers in May and is capable of reproducing both vegetatively and by seed. Although nationally rare, since it is not thought to be declining it is currently listed as Least Concern in the England Vascular Plant Red List (Stroh et al., 2014).

Viola rupestris was first recognised in Britain from upper Teesdale (v.c.66, Co. Durham) by James Backhouse in 1862 (Backhouse, 1884), then almost a century later, it was found on Long Fell near Brough (Valentine & Harvey, 1960) and later at Arnside Knott (both in v.c.69, Westmorland). Although the colony at the latter site was quite small (c.50 plants), the fact that it was well removed from the two other sites held promise of the species being found even further afield. The extensive karst upland of Yorkshire’s Craven District was cited as one possible habitat. And so, it proved when on 25 May 1976 the species was discovered on Ingleborough by BSBI member Jeremy Roberts (Roberts, 1977).

Significant numbers of plants initially were found at 384 metres altitude along the popular Selside to Clapham bridleway some 4km south-east of the Ingleborough summit. Subsequent searches later revealed a scattered distribution throughout the Moughton Fell (SD788708) area, around the skyline perimeter of Crummackdale, above the southfacing Robin Proctor Scar (SD763697) and the nearby Norber Brow. Small populations were later recorded at Smearsett Scar (SD800678), overlooking the hamlet of Feizor, some 2km due south of the nearest specimens on the wider Ingleborough massif.

Apart from a smattering of other records added (by Brian Burrows and others) from the Sulber Pasture area between the 1970s and 2019, all V. rupestris records prior to the present survey existed outwith the Ingleborough NNR boundary.

I consulted both Jeremy Roberts and Brian Burrows. The take-home message from these conversations was that, other than records having

Viola rupestris (Teesdale Violet) showing a plant flower and a dehisced fruit.

A plant next to a 5p coin.

casual remarks like ‘100+ plants scattered among stony grassland’ or ‘about 12 plants on west side of path,’ neither of them, nor to their knowledge anyone else, had ever made an attempt to establish the full extent of the Ingleborough population. A comprehensive survey was the answer. I had only recently been signed up as a volunteer with Natural England at Colt Park, and since I was looking for a project to get my teeth into, my interest was piqued.

And so with the seed thus sown, and motivated by Colin’s timely carrot on a stick, I finally picked up the gauntlet. Though there was clear evidence for significant numbers elsewhere on Ingleborough, the rationale for confining the search solely to those parts of the SSSI comprising the reserve was simple. With a total area of over 1,000 hectares this would present challenge enough. Furthermore, once completed the results would furnish Natural England, the Yorkshire Dales National Park, the BSBI and other conservation bodies with a baseline population count to inform any future surveys.

During planning, and to gain a sense of the task to come, and so devise the best strategy for conducting the survey, I made tentative visits to the Sulber Pasture (Compartment 34 of the reserve) around May and June 2020. Some initial Viola specimens were found around this time, and Jeremy Roberts later confirmed these to be V. rupestris. Thus, with my ‘eye in’ the survey proper could commence. For this I chose to start in the first week in August. Wherever the landscape presented obvious salient features I used these as a mental datum with which to divide the area into smaller, more manageable plots. Failing that, pennants and poles were employed to mark out suitably sized plots. Once each was completed I moved on in a kind of rolling survey. By this means I could obviate duplication or overlooking plants altogether. Locations were logged using a Garmin eTrex 10 or Garmin GPS60 and the results entered into the Natural England floral database.

Sulber was my starting point as this appeared to hold out the best prospects, having as it did the largest area of optimum habitat; other areas were more extensive, but were mainly acid heath with only small outcroppings of the Yoredale Series limestone exposed along the 600 metre contour. Other reserve compartments presented minimal or no suitable habitat and therefore could be either dismissed altogether from the survey or required little investigation. Sulber is an exposed tract presenting a flat to slightly undulating short calcareous grassland with areas of clitter, bankings, shallow screes and calcareous flushes. The compartment also has ‘islands’ of ericaceous ground with Calluna vulgaris (Heather), Potentilla erecta (Tormentil) and Narthecium ossifragum (Bog Asphodel).

The elements were a dominant factor in conducting the survey. When inclement there was little to prevent the scarifying winds raking the area; in mid-summer, however, with Three Peaks walkers visible at a comfortable remove, only the welcoming refrain of the skylark disturbed the solitude as work progressed. Eighteen expeditions were necessary to complete the investigation of this compartment, which in due course revealed 17,240 plants spread across 2,041 GPS locations.

As autumn was ushered in and plant numbers steadily climbed, it then dawned that the reserve might well be the repository for a very significant population. By late October, the weather, not to mention increasingly tighter Covid-19 restrictions, forced a temporary cessation. By this time the total count had exceeded 20,000 plants.

It was not until May 2021 that surveying restarted, with daily totals ranging from less than one hundred upwards as the remaining compartments of the reserve were systematically investigated. The imperative then was to complete the work by mid-autumn before the onset of the first wintery conditions or my suffering knees gave out altogether. As October came around again the last area was finally in the bag and the total number of plants weighed in at 39,699.

The Ingleborough population of V. rupestris displays variations in the diagnostic characters, in particular the degree of indumentum. The typical fuzz of short hairs on the peduncles, petioles and capsule was found to vary considerably. On the petioles in particular, it ranged from dense – imparting a grey appearance when viewed with the naked eye – to slightly or totally glabrous from one plant to another, even petiole to petiole on a single rosette. That many Ingleborough plants are largely or completely glabrous is a not widely appreciated fact.

Though still retaining the oft-quoted garden trowel appearance due to the turned-up margins, leaf blades of more mature plants, rather than having the usual ovate form, were sometimes found to be far more pointed. The leaves can be grey-green or dark green and often red- or dull purple-tinged in more mature plants; the lamina slightly cordate or ± truncate as opposed to being strongly cordate as in V. riviniana (Common Dog-violet).

The species consists of a non-flowering rosette from which lateral, decumbent flowering/fruiting stems are produced. The latter are often masked by the substrate and difficult to determine. As these ancillary rosettes do not themselves take root they therefore do not become discrete specimens. For this reason I tended to disregard rosettes in close proximity (2–3cm) as belonging a single plant.

Since the majority of flowers are cleistogamous, only about 1% of plants actually produce open blooms in any given year; these generally appearing around May. Those I saw in flower had petals with a background colour of a paler blue-violet than in V. riviniana. Also contrary to the latter species, the spur is shorter and conical, with a rounded tip lacking the obvious notch. After the flowering season was over and capsules ripened, the buff colour of the dehisced capsule valves was a feature that often drew my attention among the sward when counting individuals.

The NNR is composed of 43 compartments. Of these discrete areas V. rupestris was present in only five, all as it happens located to the south-east of the Ingleborough summit plinth (Figure 1). Out of the total plants counted the highest density was found in Compartment 38B (The Moor) with an average 857.7 plants per hectare, the least in Compartment 37B (High Brae) averaging 32 plants per hectare (Table 1). A close examination of the density map will reveal that it does not bear out the averages referred to above. An obvious reason for this is that species density in any compartment is largely determined by habitat. The explanation for the discrepancy, therefore, is that V. rupestris was found – albeit at lower density levels – over most of The Moor, while on large swathes of Sulber and High Brae there are none. Furthermore, V. rupestris on Sulber mostly keeps to the areas frequented by calcicoles such as Primula farinosa, while avoiding large areas dominated by acid heath; the latter obvious on the density map as blanks towards the west and south of Sulber compartment. Likewise, the eastern half of High Brae comprises of terrain wholly unsuited to the species.

Although the published floras state that the species can occur up to 600 metres altitude, all the plants found in the present survey occurred on the Great Scar limestone exposed between the 331 and 414 metre contours. Typically, the population ranged from the scattered and isolated few to colonies of over 100 plants, especially so on Sulber and on The Moor where concentrations proved astonishing.

The ecological preference of V. rupestris is for short, open calcareous turf on thin stony soils, especially on the weather-strafed edges of bankings; in areas of accumulated frost-shattered small stones

Figure 1. Density of Viola rupestris (Teesdale Violet) at Ingleborough NNR.

Table 1. Total counts of Viola rupestris (Teesdale Violet) at Ingleborough NNR. Sulber (34) High Brae

(37B) Juniper Gill The Moor (38A) The Moor (38B)

Area (ha) 117.5 75.6 11.04 11.9 11.9

Total plants

17,240 2426 1682 8144 10,207 Total locations 2041 425 281 859 1099 Plants as % of NNR total 43.4 6.1 4.2 20.5 25.7 Density per compartment (plants per ha) 146.7 32.1 152.4 684.4 857.7

(clitter) resulting from degradation of the bedrock through winter’s repeated freeze-thaw cycles; on slopes of calcareous glacial drift and also gently inclined fine scree of usually not more than 30 degrees. A smaller number of specimens could be accounted for among block scree and also, but more rarely, on pavements among small amounts of clitter, or where a little turf or humus had accumulated in shallow depressions and fissures on clint tops. The most common associated bedfellows were Viola riviniana, Viola hirta (Hairy Violet), Primula farinosa, Linum catharticum (Fairy Flax), Carex flacca (Glaucous Sedge), Sesleria caerulea (Blue Moor-grass), Campanula rotundifolia (Harebell) and Thymus drucei (Wild Thyme).

That there should be such a high density of the species on the limestone plateaux of southeastern Ingleborough comes as no surprise given the equally high incidence of optimum habitat. On these plateaux, as in all three of its other English locations, V. rupestris favours a habitat tending to the more exposed; Sulber, for instance, presents a

landscape offering little impediment to the prevailing westerlies.

Significant numbers of V. rupestris on Widdybank Fell in Teesdale were lost due to the flooding of Cow Green Reservoir (1967–1971). Seeking some indication of present population for comparison with those found in this survey, a conversation with Martin Furness (Manager of Moorhouse Reserve) advised the best estimate of numbers to be around 10,000 plants, similar to that stated by Scott (2016, p.150). Similar, best guess figures for the population on Long Fell as I understand it is probably in the hundreds rather than 1000s, while the outlying colony at Arnside Knott had only fifty or so specimens, though some plants have apparently been lost here through under-grazing and the resulting increase in Sesleria caerulea.

Given the considerable size of the Craven population and the difficulties of determining the hybrid between Viola rupestris and V. riviniana (V. × burnatii) (Jonsell et al., 2000; Roberts, 2020), it is possible that the occasional hybrid might have been mistaken for V. rupestris. However, since the hybrid has a preference for deeper soils, and denser turf, than that tolerated by V. rupestris, it was judged unlikely to occur in the present survey area.

It is now clear from the present investigation, that with a population in excess of 39,000 plants, Ingleborough has emerged as a major population locus for the species, rivalling, if not exceeding, that of Teesdale in importance. How might one account for such an abundant and apparently stable population? Lacking any previous surveys for comparison makes it impossible to equate the large numbers of plants to the changeover to cattle-only grazing; indeed a density of plants far exceeding that on Sulber was recorded on The Moor (Compartments 38A/38B) where sheep have only recently been removed.

However, for a species requiring open areas of bare soil for seedlings to establish it is easy to see how ground so produced by poaching would benefit population growth. Furthermore, based on the density of plants encountered on the reserve, it is not unreasonable to believe, were one to allow for those populations known – and anticipated – to exist on the wider Ingleborough area but outside the reserve, that another 10,000–30,000 plants could possibly be added.

I would like to thank Andy Hinde and the staff of Natural England at Colt Park for support and loan of a GPS, Clare Langrick and Mark Wills (North & East Yorkshire Ecological Data Centre) for production of the map, Edward Easton for forbearance in dealing with the volume of records the survey has furnished for the NE floral database and Jeremy Roberts for initial guidance in identification, for proof-reading the initial draft of this article, and offering useful commentary and constructive criticism.

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Vill. in Mid-W. Yorkshire. Watsonia 11: 385–386. Roberts, F.J. 1998. Viola rupestris/V. riviniana/V. hirta. In:

T.C.G. Rich & A.C. Jermy (eds), Plant Crib, pp.109–111.

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Plant Red List for England. Botanical Society of Britain and

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