Vice-county 35 (Monmouthshire)

HomeRecordingVice-county explorerVice-county 35 (Monmouthshire)

Old Red Sandstone blocks below the landslip on Ysgyryd Fawr

Key sites and key habitats for rare bryophytes

Rare and scarce bryophytes have been recorded at numerous localities across the entire Vice County and are doubtless present at many others. Five locations stand out as being especially important for bryophyte conservation in the county; all are, entirely or partially, protected by SSSI and/or SAC designations. Many other sites are also of significant bryophyte conservation importance and their exclusion from this list certainly does not mark them as unimportant.

ST59 Blackcliff, Wyndcliff & Chepstow Woods

Small pieces of limestone on the woodland floor in the lower Wye Valley are home to Blindiadelphus campylopodus

The steeply sloping woods of the lower Wye Valley, which hold several tall crags of Carboniferous Limestone, stretch from Tintern to Chepstow, a distance of more than 6km. Two cliffs are of particular importance for their calcicolous bryophytes: the northeast-facing Black Cliff and the south-facing Wynd Cliff. Numerous other outcrops are known to support interesting species, despite the difficulty of accessing many of them. Two of the three Nationally Rare species that have been recorded from this area appear to be extinct: Anomodon longifolius was last recorded from “near Tintern” in 1925 and Bryum turbinatum was collected from a roadside in 1891. A third Nationally Rare moss, Blindiadelphus campylopodus, remains a widely scattered rarity of small pieces of limestone between Black Cliff and Apostles Rocks and the lower Wye Valley is its UK headquarters. Despite much recent searching, there remains a possibility that A. longifolius persists in the area; B. turbinatum has surely vanished, indeed it has not been recorded in Britain since 1947.

Despite these losses, the calcareous woods of the lower Wye Valley are home to a number of uncommon bryophytes. Most notable is the B. campylopodus mentioned above. Limestone provides the habitat for a few scattered patches of Cololejeunea rosettiana as well as its lookalike C. calcarea and an abundance of Marchesinia mackaii. Serpoleskea confervoides, Campylophyllopsis calcarea, Eurhynchiastrum striatulum and Leptobarbula berica also occur, usually in rather small quantity, on shaded limestone. An exposed section of the Wynd Cliff supports a colony of Schistidium elegantulum ssp. elegantulum; the quarry below the cliffs holds Gymnostomum viridulum; the stream running through Cave Wood is lined with Fissidens rivularis and provides sufficiently humid conditions for Lophocolea fragrans and Trichocolea tomentella. Away from the Wye Valley, the limestone west of Chepstow is also of conservation importance. Great Barnets Woods holds Thuidium recognitum at its only south Wales site, the Mounton area held moribund Anomodon longifolius until at least the early 2000s and Scorpiurium circinatum, whilst Daggers Hill supports Blindiadelphus campylopodus and Serpoleskea confervoides.

SO20/21 The Blorenge, Cwm Ifor & Gilwern Hill

Cwm Ifor – a stream cutting through Carboniferous Limestone

This large area – stretching for about 8km from Gilwern Hill to Mynydd-y-garn-fawr – forms a geological entity connected by the Carboniferous limestone that outcrops at several places along its northern and eastern sides. Above this limestone is a capping of Millstone Grit, which forms beds of block-scree on the Blorenge and Mynydd-y-garn-fawr ridges. The geological diversity of the area means that it has an exceptionally long bryophyte list, and three of its component tetrads have the highest totals of any in the county. The area’s bryophytes fall into two camps: the limestone supports many Nationally Scarce species, whilst the sandstone and Millstone Grit support upland and Atlantic species of biogeographical interest.

The natural limestone outcrops on the eastern edge of the Blorenge, the gorge of Cwm Ifor, and a few other crags nearby, are known to support a rich bryophyte flora; those on Gilwern Hill have not been explored in such detail. The tiny Seligeria mosses are well-represented on almost all of the natural limestone: S. pusilla is locally frequent on most outcrops; S. acutifolia is occasional on three; S. donniana appears to be restricted to one outcrop on Gilwern Hill; and S. patula has been recorded on a seeping cliff on the east side of the Blorenge. The sheltered limestone of the Cwm Ifor gorge holds Platydictya jungermannioides and Bartramia ithyphylla, whilst Funaria muhlenbergii is at its only VC locality on a limestone boulder nearby. Most of the limestone at Gilwern Hill has been quarried and the resultant calcareous spoil heaps provide suitable conditions for Scapania cuspiduligera and Rhodobryum roseum. The Scapania also occurs in small quantity in a quarry at Garn-ddyrys, a kilometre to the east. Thuidium assimile is frequent on calcareous quarry spoil on both sides of the Blorenge ridge.

A base-rich sandstone crag on the north face of the Blorenge supports Encalypta ciliata and Bryum zieri at their most southeasterly British locality; Bartramia ithyphylla, Mnium marginatum and Pohlia cruda near their southeasterly limit; and a number of interesting associates including Cololejeunea calcarea, Lejeunea patens, Bryum ‘subelegans’ (a gemmiferous form of B. pallens), Platydictya jungermannioides and Tortula subulata ‘var. graeffii‘. Scree beds have developed along the length of the main ridge – from the Blorenge summit to the southern end of Mynydd-y-garn-fawr (and on to Mynydd Garnclochdy to the south). These are noteworthy for a suite of liverworts that approach the south-eastern edge of their core British ranges here. Two patches of Anastrophyllum minutum and five of Lepidozia cupressina have been found so far; Bazzania trilobata and Dicranum fuscescens are slightly more widespread. Only the deepest holes in the block scree beds provide sufficiently humid conditions throughout the year for these species to occur. Tetraplodon mnioides has been found on bones on Gilwern Hill and Mynydd Garnclochdy, where sheep died after getting trapped.

Millstone Grit block scree on The Blorenge

SO22 Cwmyoy

Cwmyoy Graig is the county’s best example of dry, south-facing, Old Red Sandstone slopes, an unusual habitat that is also found at the southern ends of Bryn Arw and Ysgyryd Fawr. The most notable species here is Grimmia longirostris, which grows on a sandstone block in the central valley and is currently known from only one other site in Wales. Nearby, Leucodon sciuroides and Nogopterium gracile are abundant on sandstone blocks, whilst Rhodobryum roseum and Bryum donnianum occur in calcareous turf. The dry, south-facing slopes of the Graig support strong colonies of Microbryum curvicolle and Tortula lanceola, as well as smaller quantities of  T. caucasica (T. modica), M. davallianum and M. rectum. Other species recorded here include Bartramia ithyphylla, Cephaloziella stellulifera, Scleropodium tourettii and Tortula subulata. A BBS visit to the sandstone block-field below the nearby Cwmyoy Darren revealed Porella arboris-vitae, Leucodon sciuroides, Nogopterium gracile and Didymodon ferrugineus. Grimmia longirostris was found here in 1998 but has not been seen since.

SO23 Tarren yr Esgob

Two thirds of Tarren yr Esgob, a 4km long, east-facing series of Old Red Sandstone crags, lies in Breconshire (VC42). Despite looking rather insignificant on the map, the Monmouthshire section of the Tarren is sufficiently extensive to support most of the species that occur across the border (Seligeria patula, Scapania calcicola and S. subalpina are the principal exceptions). The site is particularly notable as the most southeasterly locality in Britain for three scarce upland calcicoles – Bartramia halleriana, Plagiopus oederianus and Scapania aequiloba – as well as being at the edge of the range of other upland mosses such as Bryum julaceum, Distichium capillaceum, Isopterygiopsis pulchella and Pohlia elongata. Brachydontium trichodes is scattered on the crag as well as on sandstone rocks in the valley below, whilst Blepharostoma trichophylla, Fissidens osmundoides, Frullania fragilifolia, Jungermannia subelliptica and Tetrodontium brownianum remain unrecorded elsewhere in the Vice County.

SO51 Lady Park Wood

The principal bryological interest of this National Nature Reserve is the presence Anomodon longifolius at its only remaining Welsh site. It appears to have gone from the main limestone cliff due to a rockfall but is scattered on limestone outcrops along the Whippington Brook, which forms the border with England. This species is slightly commoner just across the border in Gloucestershire. Lejeunea mandonii has its only Welsh population on another limestone outcrop on the Monmouthshire side of the Whippington Brook. Two thriving colonies of Blindiadelphus campylopodus occupy small pieces of limestone between the NNR and Hadnock Quarry. Numerous scarce species occur in and arround the NNR, most of them associated with limestone. Serpoleskea confervoides, Campylophyllopsis calcareum and Eurhynchium striatulum are found on rocks and stones on the woodland floor; Metzgeria pubescens (at its most southerly British site), Cololejeunea rosettiana, Gymnostomum calcareum, Seligeria donniana and S. acutifolia grow together on wet limestone by the Whippington Brook; Platydictya jungermannioides is probably restricted to the drier main cliff. Other habitats nearby hold Fissidens rufulus, Gymnostomum viridulum, Orthotrichum sprucei and Platygyrium repens.

Other localities

Limestone quarry spoil supports Scapania cuspiduligera on Gilwern Hill and at Garn-ddyrys, Rhodobryum roseum and Racomitrium canescens (as well as probable Bryum elegans) on Gilwern Hill, Racomitrium canescens and Thuidium assimile in Cwm Sychan, T. assimile and Tortula  lindbergii (Tortula lanceola) on The Blorenge, and Aloina ambigua near Risca. Mounds of colliery spoil often have a rich and varied hepatic flora, including Orthocaulis floerkei, Isopaches bicrenatus (Lophozia bicrenata) and Ptilidium ciliare, and appear to be ideal for Buxbaumia aphylla (which has yet to be discovered in south Wales). Uncommon colonists of colliery spoil include Anthoceros punctatus at Blaen Bran and locally frequent Didymodon ferrugineus.

Colliery spoil adjacent to Gilwern Hill

Most of the county’s bogs have been lost through drainage or neglect, but a few key sites remain. Cleddon Bog’s Odontoschisma francisci has surely been lost, but Cephalozia connivens, Kurzia pauciflora and Mylia anomala remain; two mounds of Polytrichum strictum, at Garn-yr-erw and on The Blorenge, have somehow escaped burning; Waun Afon holds a little Splachnum ampulaceum and some Scapania paludicola; a bog on Rhymney Hill has S. ampulaceum, Scapania paludicola and Odontoschisma fluitans. An acid-flushed Sphagnum mire near Maesycwmmer supports Barbilophozia kunzeana (at its most southerly British site) and S. paludicola; there must be other suitable habitat for these rare species elsewhere in the west of the county. Calypogeia azurea has an outlying population on a trackside bank in the southern Black Mountains on Bal Mawr, close to some of the county’s richest flush complexes with Calliergon giganteum, Mesoptychia bantriensis, Scorpidium cossonii, S. revolvens and S. scorpioides. Riccardia incurvata and Sphagnum platyphyllum were recently collected new to VC35 in flushes in the northern Llanthony Valley.

The crags of western Monmouthshire hold locally frequent species of acid sandstone, including Polytrichastrum alpinum, Racomitrium aquaticum and Rhabdoweisia crispata and R. fugax. Schistidium platyphyllum is remarkably frequent in several of the western rivers, including the Rhymney, Sirhowy and Ebbw. Nardia compressa has its only known county site in Cwm Carn, and the western mosses Entosthodon attenuatus and Pohlia camptotrachela have their only known sites in Cwm Celyn.

A rich assemblage of epiphytes occurs on alders and willows by slow, silty rivers, and is well-developed by the Usk, Monnow, Trothy, Wye and a few of their tributaries. The rarest member of this assemblage, Myrinia pulvinata, has been noted twice on the Usk, whilst more regular components include O. sprucei and what appears to be the ‘subinermis’ form of Tortula subulata. The vertical banks of eroding sections of the river are a key habitat for Hennediella stanfordensis, Epipterygium tozeri and Pohlia lescuriana¸ and some of the Mnium marginatum on silty riverbanks may be ‘var. dioicum’ although it seems steadfastly non-fertile. Llandegfedd Reservoir supports several million plants of Riccia cavernosa as well as Ephemerum crassinervium subsp. sessile and Weissia rostellata when water levels are low, whilst Wentwood Reservoir holds Ephemerum crassinervium subsp. rutheanum (Ephemerum hibernicum), at one of its two British sites, and W. rostellata.

The Wye Valley Woodlands hold disjunct populations of species such as Syzygiella autumnalis at Black Brook, Plagiochila spinulosa and Solenostoma paroicum at Cleddon Shoots, and Jubula hutchinsae in Bargain Wood, Manor Brook and Cleddon Shoots. Blasia pusilla is bizarrely rare on forestry rides, with single records from Reddings Inclosure near the Forest of Dean and Gwenffrwd Forestry near the Sugarloaf. The only remaining colony of Pogonatum nanum is on a forestry track in Gurlos Grove near Tintern, and Schistostega pennata has been found under a boulder near Trellech Hill Quarry.

The boulder-strewn cascade at Cleddon Shoots

The church roofs of Monmouthshire are a key bryophyte habitat that has been ignored by conservationists for many years. South-facing Old Red Sandstone tiles, here and in neighbouring Herefordshire, support Grimmia laevigata, G. ovalis and Hedwigia ciliata. The Grimmia spp. are widespread in the county but H. ciliata is known from just three roofs. Llangua Church in north-easternmost Monmouthshire is the easiest site at which to pay one’s respects to these mosses because they occur at head height on the porch. Re-roofing of buildings with slate or artificial tiles continues to destroy colonies of these rare mosses and an inevitable conclusion is that all four species have undergone catastrophic declines in recent history, as locally-quarried tiles have been replaced as the most readily available roofing material.

Llangua Church is the best site in VC35 for the rare mosses of stone roof tiles

The bryophytes of arable land were studied in detail by SBAL in the early 2000s. Monmouthshire’s arable fields appear to be a key locus for Phaeoceros carolinianus in Britain and it is recorded from at least 10 fields in the county. Anthoceros agrestis is a constant companion of P. carolinianus in Monmouthshire fields and is a little more widespread in the county, whilst P. laevis is very sparsely distributed. Fossombronia caespitiformis, Weissia rostellata and W. squarrosa have been recorded in arable near Dingestow along with single tufts of Didymodon tomaculosus and Ephemerum crassinervium subsp. sessile.

Grotting along the A465 verge near Abergavenny in early 2020 revealed Didymodon australasiae, which is surely overlooked elsewhere. Urban parks are being colonised by more and more epiphytes, and recent recording in Newport has produced several records of Leucodon sciuroides and Pylaisia polyantha. Orthotrichum pallens has been found in a hedge at Dingestow, O. pumilum in a hedge east of Newport, and O. schimperi on an Ash in an Abergavenny park, indicating how rare species can pop up almost anywhere.

Anthoceros agrestis among mixed arable mosses at Dingestow

Sam Bosanquet, December 2020

Local flora

Sam Bosanquet is recording for a Bryophyte Flora of Monmouthshire, keeping all records at 6- to 8-figure Grid Reference accuracy. All records in Excel format would be welcome!