Ceunant Dulyn

Site of Special Scientific Interest · 53.1981, -3.8634

Open in the interactive map →

Also within

Clwyd County Eryri / Snowdonia National Park

Habitats

Bracken scrub, Fast flowing river and stream

Geology & landscape

Geological Feature: Gorge / Ravine · Geological Period: Ordovician

Landscape processes: Fluvial, Volcanic / Igneous

Description

Description A wooded river valley and ravine on the Afon Dulyn. The underlying rocks are a mixture of acidic Ordovician sediments and calcareous pumice tuff; this is reflected by the soil and vegetation types. Acid soils support oak Quercus petraea and birch Betula pubescens woodland with a sparse shrub layer and a ground flora with such species as bracken Pteridium aquilinum and wavy hair grass Deschampsia flexuosa. On more basic soils, oak again dominates, but with ash Fraxinus excelsior, wych elm Ulmus glabra and alder Alnus glutinosa. A shrub layer including hazel Corylus avellana occurs and a ground flora rich in such species as creeping buttercup Ranunculus repens, wild Angelica Angelica sylvestris, sanicle Sanicula europaea and male fern Dryopteris filix-mas. The Atlantic bryophyte flora is only moderately rich. Although high humidity is retained within the gorge, flow in the river is affected by the Dolgarrog Hydro-electric scheme. Remarks: Within the Snowdonia National Park.

Species mentioned

English name
search for this in other sites		 Latin name
search with Google		 IUCN / Red List Type Family
male fern Dryopteris filix-mas LC fern dryopteridaceae
bracken Pteridium aquilinum LC fern dennstaedtiaceae
wavy hair grass Deschampsia flexuosa Not listed in GB list grass poaceae
wild angelica Angelica sylvestris LC herb apiaceae
creeping buttercup Ranunculus repens LC herb ranunculaceae
sanicle Sanicula europaea LC herb apiaceae
alder Alnus glutinosa LC tree salicaceae
downy birch Betula pubescens LC tree betulaceae
hazel Corylus avellana LC tree corylaceae
ash Fraxinus excelsior LC tree oleaceae
sessile or durmast oak Quercus petraea LC tree fagaceae
wych elm Ulmus glabra LC tree ulmaceae

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
Scarce vapourer
Orgyia recens		 Endangered Alnus glutinosa, Betula spp., Corylus avellana, Quercus spp., Ulmus spp.
White-letter hairstreak
Satyrium w-album		 Endangered Ulmus glabra, Ulmus spp.
The sprawler
Asteroscopus sphinx		 Vulnerable Betula spp., Corylus avellana, Fraxinus excelsior, Quercus spp., Ulmus spp.
Broom moth
Ceramica pisi		 Vulnerable Betula spp., Pteridium aquilinum, Ulmus spp.
Mottled umber
Erannis defoliaria		 Vulnerable Betula spp., Corylus avellana, Quercus spp., Ulmus spp.
The lackey
Malacosoma neustria		 Vulnerable Corylus avellana, Quercus spp., Ulmus spp.
Pale brindled
Phigalia pilosaria		 Vulnerable Alnus glutinosa, Betula pubescens, Corylus avellana, Fraxinus excelsior, Quercus spp., Ulmus glabra
Early moth
Theria primaria		 Vulnerable Quercus spp.
Pale eggar
Trichiura crataegi		 Vulnerable Betula spp., Corylus avellana, Quercus spp.
Oak hook-tip
Watsonalla binaria		 Vulnerable Quercus petraea
Flounced chestnut
Agrochola helvola		 Near Threatened Betula spp., Quercus spp., Ulmus spp.
Beaded chestnut
Agrochola lychnidis		 Near Threatened Ranunculus spp.
Garden tiger
Arctia caja		 Near Threatened Pteridium aquilinum
Dusky-lemon sallow
Cirrhia gilvago		 Near Threatened Ulmus glabra
The sallow
Cirrhia icteritia		 Near Threatened Ulmus glabra
Dingy mocha
Cyclophora pendularia		 Near Threatened Alnus glutinosa
Brindled ochre
Dasypolia templi		 Near Threatened Angelica sylvestris
Kentish glory
Endromis versicolora		 Near Threatened Alnus glutinosa, Betula pubescens
Large thorn
Ennomos autumnaria		 Near Threatened Alnus glutinosa, Betula spp., Corylus avellana, Quercus spp., Ulmus spp.
September thorn
Ennomos erosaria		 Near Threatened Betula spp., Quercus spp.
Dusky thorn
Ennomos fuscantaria		 Near Threatened Fraxinus excelsior
Autumnal rustic
Eugnorisma glareosa		 Near Threatened Betula spp.
Grey pug
Eupithecia subfuscata		 Near Threatened Angelica sylvestris
White-spotted pug
Eupithecia tripunctaria		 Near Threatened Angelica sylvestris
Double dart
Graphiphora augur		 Near Threatened Betula spp., Quercus spp., Ulmus spp.
Swallowtail papilio
Papilio machaon		 Near Threatened Angelica sylvestris
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

W25 — Bracken scrub

Pteridium aquilinum-Rubus fruticosus underscrub

Matches 4 species from the description above: Angelica sylvestris, Dryopteris filix-mas, Fraxinus excelsior, Pteridium aquilinum

Hedera helix, Acer pseudoplatanus, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Sambucus nigra, Ulex europaeus, Crataegus monogyna, Prunus spinosa, Luzula multiflora, Mnium hornum, Brachythecium rutabulum, Kindbergia praelonga, Angelica sylvestris, Conopodium majus, Heracleum sphondylium, Arum maculatum, Cirsium arvense, Lonicera periclymenum, Silene dioica, Stellaria holostea, Mercurialis perennis, Geranium robertianum, Glechoma hederacea, Teucrium scorodonia, Hyacinthoides non-scripta, Chamerion angustifolium, Circaea lutetiana, Digitalis purpurea, Rumex acetosa, Anemone nemorosa, Ficaria verna, Potentilla erecta, Rosa arvensis, Rosa canina, Rubus fruticosus agg., Rubus idaeus, Galium aparine, Galium mollugo sens.lat., Galium saxatile, Urtica dioica, Viola riviniana, Agrostis capillaris, Anthoxanthum odoratum, Arrhenatherum elatius, Dactylis glomerata, Festuca rubra, Holcus lanatus, Holcus mollis, Poa trivialis, Pteridium aquilinum, Dryopteris dilatata, Dryopteris filix-mas

A14 — Fast flowing river and stream

Myriophyllum alterniflorum community

Isolepis fluitans, Juncus bulbosus, Fontinalis antipyretica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Lemna minor, Callitriche stagnalis, Littorella uniflora, Potamogeton filiformis, Potamogeton gramineus, Potamogeton natans, Ranunculus peltatus, Chara spp., Nitella hyalina

A17 — Chalk river and stream, Fast flowing river and stream

Ranunculus penicillatus ssp. pseudofluitans community

Berula erecta, Nasturtium officinale, Elodea canadensis, Lemna minor, Callitriche stagnalis, Veronica beccabunga, Polygonum amphibium, Polygonum hydropiper, Potamogeton crispus, Potamogeton pectinatus, Ranunculus penicillatus ssp. pseudofluitans

A18 — Fast flowing river and stream

Ranunculus fluitans community

Fontinalis antipyretica, Fontinalis squamosa var. curnowii, Myriophyllum alterniflorum, Myriophyllum spicatum, Elodea canadensis, Mentha aquatica, Lemna gibba, Lemna minor, Potamogeton perfoliatus, Ranunculus fluitans, Glyceria fluitans, Phalaris arundinacea

A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream

Potamogeton natans community

Schoenoplectus lacustris, Juncus bulbosus, Sparganium angustifolium, Sparganium erectum, Sparganium minimum, Alisma plantago-aquatica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Elodea canadensis, Lemna minor, Lemna trisulca, Nymphaea alba, Callitriche platycarpa, Callitriche stagnalis, Littorella uniflora, Potamogeton natans, Ranunculus trichophyllus, Glyceria fluitans, Chara subspinosa