Cwm Merddog Woodlands

Site of Special Scientific Interest · 51.7522, -3.1779

Also within

Gwent County

Geology & landscape

Landscape processes: Glacial

Description

Description The Cwm Merddog Woodlands comprise an extensive area of beech Faqus sylvatica woodland near the westerly limit of its geographical range and part of the site is also the highest known station for beech in Britain. Cwm Merddog Woods also has interesting transition zones between beech and alder Alnus glutinosa dominated communities in areas of impeded drainage. The site comprise two blocks of woodland below Mynydd Carn y Cefn to the south of Ebbw Vale. The main block, Cwm Merddog Wood is located on the middle and lower west and east facing slopes of the Nant Merddog. Whilst Coed Ty'n y gelli is an outlier located at an altitude of 380 m -460 m above sea level to the north and east. Both woodland blocks are located on soils derived from underlying Lower Coal Measures and from material which has fallen from the Pennant Sandstones above. In Cwm Merddog Wood, the free draining soils of the steep upper slopes support areas of beech coppice and coppice-with-standards with a characteristic ground flora which includes the locally distributed broad-leaved helleborine Epipactis helleborine. The lower slopes have extensive areas of acid flushes with an open carr community dominated by alder and willows Salix spp. These wetter areas and flushes have a rich flora of mosses, ferns and flowering plants including a number of interesting species that have not previously been recorded for this part of the county, eg. narrow buckler-fern Dryopteris carthusiana, greater tussock-sedge Carex paniculata and the heath spotted-orchid Dactylorhiza maculata. The Coed Ty'n y gelli outlier on the upper slopes is an area of coppiced beech woodland growing at the limit of its altitudinal range. The trees in this block are stunted and gnarled in appearance and large areas of the canopy are less than 2 m in height. Additional species within the canopy of both woodland blocks include scattered individuals of sessile oak Quercus petraea, hazel Corylus avellana, hawthorn Crataegus monogyna and birch Betula pendula.

Species mentioned

English name
search for this in other sites
Latin name
search with Google
IUCN / Red List Type Family
narrow buckler fern Dryopteris carthusiana LC fern dryopteridaceae
heath spotted orchid Dactylorhiza maculata LC herb orchidaceae
broad-leaved helleborine Epipactis helleborine DD herb orchidaceae
greater tussock sedge Carex paniculata LC sedge cyperaceae
hawthorn Crataegus monogyna LC shrub rosaceae
alder Alnus glutinosa LC tree salicaceae
birch Betula pendula LC tree betulaceae
hazel Corylus avellana LC tree corylaceae
sessile or durmast oak Quercus petraea LC tree fagaceae

Insects to look out for

These moths, butterflies and beetles are known to feed on plants recorded at this site, and carry a notable UK conservation status — but a host-plant being present doesn't mean the insect has actually been recorded here. Treat this as "worth watching for," not a confirmed sighting.

SpeciesStatusVia host-plant
Oak lutestring
Cymatophorina diluta
Endangered Quercus petraea
Figure of eight
Diloba caeruleocephala
Endangered Crataegus spp.
The lappet
Gastropacha quercifolia
Endangered Crataegus monogyna
Scarce vapourer
Orgyia recens
Endangered Alnus glutinosa, Betula spp., Corylus avellana, Crataegus spp., Quercus spp.
Mouse moth
Amphipyra tragopoginis
Vulnerable Crataegus spp.
The sprawler
Asteroscopus sphinx
Vulnerable Betula spp., Corylus avellana, Crataegus spp., Quercus spp.
Broom moth
Ceramica pisi
Vulnerable Betula spp.
Mottled umber
Erannis defoliaria
Vulnerable Betula spp., Corylus avellana, Crataegus spp., Quercus spp.
The lackey
Malacosoma neustria
Vulnerable Betula pendula, Corylus avellana, Crataegus monogyna, Quercus spp.
Pale brindled
Phigalia pilosaria
Vulnerable Alnus glutinosa, Betula pendula, Corylus avellana, Crataegus monogyna, Quercus spp.
Early moth
Theria primaria
Vulnerable Crataegus monogyna, Quercus spp.
Pale eggar
Trichiura crataegi
Vulnerable Betula spp., Corylus avellana, Crataegus monogyna, Quercus spp.
Oak hook-tip
Watsonalla binaria
Vulnerable Betula pendula, Quercus petraea
Flounced chestnut
Agrochola helvola
Near Threatened Betula spp., Crataegus monogyna, Quercus spp.
Beaded chestnut
Agrochola lychnidis
Near Threatened Crataegus monogyna
Grey chi
Antitype chi
Near Threatened Crataegus monogyna
Dingy mocha
Cyclophora pendularia
Near Threatened Alnus glutinosa
Kentish glory
Endromis versicolora
Near Threatened Alnus glutinosa, Betula pendula
Large thorn
Ennomos autumnaria
Near Threatened Alnus glutinosa, Betula spp., Corylus avellana, Crataegus spp., Quercus spp.
September thorn
Ennomos erosaria
Near Threatened Betula spp., Quercus spp.
Autumnal rustic
Eugnorisma glareosa
Near Threatened Betula spp.
Grey pug
Eupithecia subfuscata
Near Threatened Crataegus monogyna
Double dart
Graphiphora augur
Near Threatened Betula spp., Crataegus spp., Quercus spp.
Clay fan-foot
Paracolax tristalis
Near Threatened Quercus spp.
Frosted green
Polyploca ridens
Near Threatened Quercus petraea
White prominent
Leucodonta bicoloria
Regionally Extinct Betula spp.

Host-plant data: Cook et al. (2025), Traits data for the butterflies and macro-moths of Great Britain and Ireland, 2024, UK Centre for Ecology & Hydrology / Butterfly Conservation; and Padovani et al. (2020), Database of Insects and their Food Plants (DBIF), UK Centre for Ecology & Hydrology (both Open Government Licence). Contains data supplied by UK Centre for Ecology & Hydrology.

Plant communities

W12 — Beech wood

Fagus sylvatica-Mercurialis perennis woodland

Matches 3 species from the description above: Betula pendula, Corylus avellana, Crataegus monogyna

Hedera helix, Acer pseudoplatanus, Ilex aquifolium, Betula pendula, Betula pubescens, Carpinus betulus, Corylus avellana, Fagus sylvatica, Quercus robur, Aesculus hippocastanum, Fraxinus excelsior, Prunus avium, Sorbus aria, Taxus baccata, Ulmus glabra, Buxus sempervirens, Sambucus nigra, Viburnum lantana, Viburnum opulus, Euonymus europaeus, Cornus sanguinea, Ligustrum vulgare, Clematis vitalba, Crataegus monogyna, Daphne laureola, Carex flacca, Carex sylvatica, Mnium hornum, Plagiomnium undulatum, Fissidens taxifolius, Brachythecium rutabulum, Kindbergia praelonga, Thamnobryum alopecurum, Tamus communis, Anthriscus sylvestris, Heracleum sphondylium, Sanicula europaea, Arum maculatum, Arctium minus, Mycelis muralis, Solidago virgaurea, Cynoglossum officinale, Alliaria petiolata, Campanula trachelium, Lonicera periclymenum, Silene dioica, Euphorbia amygdaloides, Mercurialis perennis, Geranium robertianum, Hypericum hirsutum, Iris foetidissima, Ajuga reptans, Glechoma hederacea, Lamiastrum galeobdolon, Stachys sylvatica, Teucrium scorodonia, Allium ursinum, Hyacinthoides non-scripta, Chamerion angustifolium, Circaea lutetiana, Epilobium montanum, Cephalanthera damasonium, Neottia nidus-avis, Neottia ovata, Veronica chamaedrys, Rumex sanguineus, Anemone nemorosa, Ficaria verna, Ranunculus bulbosus, Fragaria vesca, Geum urbanum, Rosa canina, Rubus fruticosus agg., Galium aparine, Galium mollugo sens.lat., Galium odoratum, Urtica dioica, Viola riviniana, Anisantha sterilis, Arrhenatherum elatius, Brachypodium sylvaticum, Bromopsis ramosa, Dactylis glomerata, Deschampsia cespitosa, Melica uniflora, Milium effusum, Poa nemoralis, Poa trivialis, Asplenium scolopendrium, Dryopteris dilatata, Dryopteris filix-mas

W14 — Beech wood, Wood pasture

Fagus sylvatica-Rubus fruticosus woodland

Matches 3 species from the description above: Betula pendula, Corylus avellana, Epipactis helleborine

Hedera helix, Salix caprea, Acer pseudoplatanus, Ilex aquifolium, Betula pendula, Betula pubescens, Corylus avellana, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Pinus sylvestris, Prunus avium, Sorbus aria, Sorbus aucuparia, Taxus baccata, Ulmus glabra, Sambucus nigra, Ruscus aculeatus, Ligustrum vulgare, Carex remota, Carex sylvatica, Luzula pilosa, Mnium hornum, Dicranella heteromalla, Dicranum scoparium, Fissidens taxifolius, Brachythecium rutabulum, Hypnum cupressiforme, Isothecium myosuroides, Kindbergia praelonga, Plagiothecium denticulatum, Plagiothecium undulatum, Pseudotaxiphyllum elegans, Thuidium tamariscinum, Atrichum undulatum, Polytrichum commune, Polytrichum formosum, Arum maculatum, Lonicera periclymenum, Moehringia trinervia, Stellaria media agg., Euphorbia amygdaloides, Mercurialis perennis, Hypericum pulchrum, Lamiastrum galeobdolon, Hyacinthoides non-scripta, Circaea lutetiana, Epipactis helleborine, Oxalis acetosella, Digitalis purpurea, Anemone nemorosa, Ranunculus repens, Geum urbanum, Rubus fruticosus agg., Rubus idaeus, Galium odoratum, Galium verum, Urtica dioica, Viola riviniana, Agrostis capillaris, Agrostis stolonifera, Brachypodium sylvaticum, Bromopsis ramosa, Dactylis glomerata, Deschampsia cespitosa, Deschampsia flexuosa, Holcus lanatus, Holcus mollis, Melica uniflora, Milium effusum, Poa nemoralis, Poa trivialis, Schedonorus giganteus, Pteridium aquilinum, Dryopteris dilatata, Dryopteris filix-mas

W15 — Beech wood, Wood pasture

Fagus sylvatica-Deschampsia flexuosa woodland

Matches 2 species from the description above: Betula pendula, Quercus petraea

Hedera helix, Acer pseudoplatanus, Ilex aquifolium, Betula pendula, Betula pubescens, Fagus sylvatica, Quercus hybrid, Quercus petraea, Quercus robur, Pinus sylvestris, Sorbus aucuparia, Taxus baccata, Calluna vulgaris, Rhododendron ponticum, Vaccinium myrtillus, Ruscus aculeatus, Carex pilulifera, Luzula pilosa, Luzula sylvatica, Mnium hornum, Orthodontium lineare, Dicranella heteromalla, Dicranum scoparium, Leucobryum glaucum, Hylocomium splendens, Hypnum cupressiforme, Kindbergia praelonga, Plagiothecium undulatum, Pseudotaxiphyllum elegans, Rhytidiadelphus loreus, Thuidium tamariscinum, Polytrichum formosum, Tetraphis pellucida, Calypogeia fissa, Diplophyllum albicans, Gymnocolea inflata, Lepidozia reptans, Cladonia fimbriata, Cladonia squamules, Lonicera periclymenum, Hyacinthoides non-scripta, Chamerion angustifolium, Oxalis acetosella, Rubus fruticosus agg., Melanpyrum pratense, Agrostis capillaris, Deschampsia flexuosa, Holcus lanatus, Holcus mollis, Molinia caerulea, Poa nemoralis, Blechnum spicant, Pteridium aquilinum, Dryopteris dilatata