Thorne Colliery near Doncaster

Friday 31st May 2024

Leader: Louise Hill

Louise led us on a walk around the site of the former Thorne Colliery, approximately 10 miles NE of Doncaster.  This was a joint meeting with the Doncaster Naturalists' Society.  We parked at the eastern end of Grange Road in the village of Moorends. We initially followed the public footpath, which would have led us to Thorne Moor (Thorne Moor is part of the Humberhead Peatlands National Nature Reserve), but we soon diverted from the footpath to explore the brownfield site of the former colliery. The colliery was operational between 1925 and 1956 but had operational issues throughout its life. Flooding of the mine shafts was a particular issue due to the position of the geological strata. There were proposals to resume coal mining, including as recently as the 1990s, but these were deemed uneconomic and in 2004 the pit pumps were finally switched off and the colliery headgear was demolished. Part of the site is now a solar farm, with the remainder currently being reclaimed by nature.

The site includes areas with thin soil, grassland, scrub, colliery spoil and small wet areas, offering a wide range of opportunities for wildlife. Brownfield sites are often a refuge for early-successional species that are scarce or absent from the surrounding landscape and this ‘open mosaic habitat’ is a Priority Habitat in the UK. Colliery spoil heaps can be hostile environments for many common plants but can support unusual species which are capable of adapting to these conditions. The ground water can have a high salt content due to passing through colliery spoil or mine water contamination, supporting plant species more normally associated with the coast. This may account for why we found Sea Campion (Silene uniflora) at our lunch spot.

Most members of the pea family are capable of ‘nitrogen fixing’, making them frequent colonisers of colliery spoil. They have a symbiotic relationship with bacteria that allow them to transform atmospheric nitrogen into a form that can be taken up by plants. One member of the pea family, Common Bird's-foot-trefoil (Lotus corniculatus), is the favoured food plant for caterpillars of the Dingy Skipper butterfly, and we were pleased to find both the plant and the butterfly. An advantage of today’s cool weather was that the butterflies were rather docile. Jesse found a Dingy Skipper in the grass and he was easily able to tempt it onto his hand where it stayed for some time, allowing everyone to get a close view of this more uncommon butterfly. A Common Blue butterfly, whose caterpillars also feed on Common Bird's-foot-trefoil, was equally obliging. Growing in close proximity to each other were Lesser Trefoil (Trifolium dubium), Hop Trefoil (Trifolium campestre) and Black Medick (Medicago lupulina), allowing some members to get a useful lesson in trefoil id.

We were pleased to find a number of orchids doing well on the site, with a particularly nice patch of Southern Marsh-orchid (Dactylorhiza praetermissa). There was also Common Spotted-orchid (Dactylorhiza fuchsii), Pyramidal Orchid (Anacamptis pyramidalis), Common Twayblade (Neottia ovata) and Bee Orchid (Ophrys apifera), surprisingly all in flower. Towering above the Southern Marsh-orchids, were a couple of flower spikes of the hybrid between Common Spotted-orchid and Southern Marsh Orchid (Dactylorhiza x grandis), demonstrating their hybrid vigour.

On the top of a spoil heap were several plants of Small Cudweed (Logfia minima), with the group also seeing Common Cudweed (Filago germanica) earlier in the day. On the same spoil heap was Lesser Hawkbit (Leontodon saxatilis), with Louise likening the dark margins of the sepals to ‘eyeliner’. A little further away was Parsley-piert (Aphanes arvensis).

Plants in flower today included Fairy Flax (Linum catharticum), Field Forget-me-not (Myosotis arvensis), Mouse-ear-hawkweed (Pilosella officinarum), Common Milkwort (Polygala vulgaris), Eyebright (Euphrasia agg), Cut-leaved Crane's-bill (Geranium dissectum), Dappled Hawkweed (Hieracium scotostictum), Oxeye Daisy (Leucanthemum vulgare) and Rough Hawk's-beard (Crepis biennis). Wild Strawberry (Fragaria vesca) was already in fruit, with some members sampling the produce. Also worthy of mention, but not yet in flower, were Common Centaury (Centaurium erythraea), Yellow-wort (Blackstonia perfoliata), Wild Carrot (Daucus carota), Square-stalked St John's-wort (Hypericum tetrapterum) and Perforate St John's-wort (Hypericum perforatum).

We also had the chance to learn/revise our grass id, seeing Flattened Meadow-grass (Poa compressa), Squirreltail Fescue (Vulpia bromoides), Early Hair-grass (Aira praecox), and variety of Soft-brome with hairless spikelets (Bromus hordeaceus var. leiostachys). In a wet depression in the path was Small Sweet-grass (Glyceria declinata), with Louise explaining how to look at the lemma tips to separate the different species of Glyceria.

In another puddle, Louise fished out a sample of Horned Pondweed (Zannichellia palustris), which isn’t a plant we come across very often. Perhaps it gets overlooked, as most of our party walked past this, having to retrace their steps to see the plant in situ.

There were some naturalised garden escapes present including Bearberry Cotoneaster (Cotoneaster dammeri), Hjelmqvist's Cotoneaster (Cotoneaster hjelmqvistii) and a Bridewort later confirmed as a variety of Billard's Bridewort (Spiraea x billardii var. macrothyrsa).

We thanked Louise for showing us around this interesting site. It would be interesting to know what the future holds for this former colliery. It would be a shame to lose this wildlife oasis.

Text by Susan

Photographs by Tom and Susan