Coed Cwm Cletwr
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Geology & landscape
Geological Period: Ordovician, Silurian
Description
Description This long and narrow sessile oakwood, situated along the Afon Clettwr, upstream of the village of Tre'r-ddol, overlies Silurian rocks, but is in close proximity to the Ordovician outlier of Pumlumon. The tree canopy is chiefly of sessile oak Quercus petraea, but this gives place locally to ashwood with occasional wych elm Ulmus glabra, aspen Populus tremula and small leaved-lime Tilia cordata. It is in the ashwood that the flora is richest, and where the presence of calcicole species indicates patches of lime-rich soil in a predominantly acid terrain. Similar patches occur in the two valleys Llyfnant and Einion to the north suggesting that a band of calcareous rock extends south-west from Machynlleth across all three valleys. Flowering plants (140 spp. recorded to date) are in much greater variety than in most woodlands in the district, and besides sheets of dog's mercury Mercurialis perennis and much sanicle Sanicula europaea, there is also woodruff Galium odoratum, yellow archangel Lamiastrum galeobdolon, wood speedwell Veronica montana and guelder rose Viburnum opulus. Sixteen species of fern, including oak fern Gymnocarpium dryopteris, beech fern Phegopteris connectilis and Wilson's filmy-fern Hymenophyllum wilsonii, and 90 species of mosses and liverworts have been found to date. The lichen flora is also diverse and of great interest. Of special interest is toothwort Lathraea squamaria, only known in one other locality in Ceredigion. Remarks: Most of the site is a nature reserve of the West Wales Naturalists' Trust. Partly owned by the Forestry Commission.
Species mentioned
Show the 14 species mentioned in the description, with red-list status| English name search for this in other sites |
Latin name search with Google |
IUCN / Red List | Type | Family |
|---|---|---|---|---|
| oak fern | Gymnocarpium dryopteris | NT | fern | woodsiaceae |
| Wilson's filmy-fern | Hymenophyllum wilsonii | VU | fern | hymenophyllaceae |
| beech fern | Phegopteris connectilis | LC | fern | thelypteridaceae |
| woodruff | Galium odoratum | LC | herb | rubiaceae |
| yellow archangel | Lamiastrum galeobdolon | LC | herb | lamiaceae |
| toothwort | Lathraea squamaria | LC | herb | orobanchaceae |
| dog's mercury | Mercurialis perennis | LC | herb | euphorbiaceae |
| sanicle | Sanicula europaea | LC | herb | apiaceae |
| wood speedwell | Veronica montana | LC | herb | plantaginaceae |
| gelder rose | Viburnum opulus | LC | shrub | caprifoliaceae |
| aspen | Populus tremula | LC | tree | salicaceae |
| sessile or durmast oak | Quercus petraea | LC | tree | fagaceae |
| lime small leaved | Tilia cordata | LC | tree | malvaceae |
| 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.
| Species | Status | Via host-plant |
|---|---|---|
| Oak lutestring Cymatophorina diluta |
Endangered | Quercus petraea |
| Dark bordered beauty Epione vespertaria |
Endangered | Populus tremula |
| Scarce vapourer Orgyia recens |
Endangered | Quercus spp., Ulmus spp. |
| White-letter hairstreak Satyrium w-album |
Endangered | Ulmus glabra, Ulmus spp. |
| The sprawler Asteroscopus sphinx |
Vulnerable | Populus spp., Quercus spp., Tilia spp., Ulmus spp. |
| Broom moth Ceramica pisi |
Vulnerable | Ulmus spp. |
| Scarce chocolate-tip Clostera anachoreta |
Vulnerable | Populus spp., Populus tremula |
| Mottled umber Erannis defoliaria |
Vulnerable | Populus tremula, Quercus spp., Ulmus spp. |
| Satyr pug Eupithecia satyrata |
Vulnerable | Galium spp. |
| Bedstraw hawk-moth Hyles gallii |
Vulnerable | Galium spp. |
| The lackey Malacosoma neustria |
Vulnerable | Quercus spp., Ulmus spp. |
| Pale brindled Phigalia pilosaria |
Vulnerable | Populus spp., Quercus spp., Tilia spp., Ulmus glabra |
| Early moth Theria primaria |
Vulnerable | Quercus spp. |
| Pale eggar Trichiura crataegi |
Vulnerable | Populus spp., Quercus spp. |
| Oak hook-tip Watsonalla binaria |
Vulnerable | Quercus petraea |
| No common name Zeugophora turneri |
Vulnerable | Populus tremula |
| Flounced chestnut Agrochola helvola |
Near Threatened | Quercus spp., Ulmus spp. |
| Purple emperor Apatura iris |
Near Threatened | Populus tremula |
| Minor shoulder-knot Brachylomia viminalis |
Near Threatened | Populus tremula |
| Dusky-lemon sallow Cirrhia gilvago |
Near Threatened | Ulmus glabra |
| The sallow Cirrhia icteritia |
Near Threatened | Populus spp., Ulmus glabra |
| Large thorn Ennomos autumnaria |
Near Threatened | Populus spp., Quercus spp., Ulmus spp. |
| September thorn Ennomos erosaria |
Near Threatened | Quercus spp., Tilia spp. |
| Autumnal rustic Eugnorisma glareosa |
Near Threatened | Galium spp. |
| Grey pug Eupithecia subfuscata |
Near Threatened | Populus tremula |
| Double dart Graphiphora augur |
Near Threatened | Quercus spp., Ulmus spp. |
| Clay fan-foot Paracolax tristalis |
Near Threatened | Quercus spp. |
| Frosted green Polyploca ridens |
Near Threatened | Quercus petraea |
| Scarce hook-tip Sabra harpagula |
Near Threatened | Tilia cordata |
| Dark-barred twin-spot carpet Xanthorhoe ferrugata |
Near Threatened | Galium 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.