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Henllys Bog SSSI

A small valley mire surrounded by woodland with a large and interesting flora

Valley mires are areas of water-logged peat in valley bottoms, with characteristic plant communities. Many of these wildlife-rich habitats have been lost through drainage, and they have become very rare nationally. Of the handful of valley mires left in Gwent, Henllys Bog is the best one for wildlife. Henllys Bog is actually fed by springs, and the brook that runs along the edge of the reserve does not supply it with water.



Purple moor-grass tussocks dominate the centre of the mire. In summer the striking deep pink spikes of purple-loosestrife are easily identified. Two unusual species of orchid are found on the reserve – the rare marsh helleborine and the fragrant orchid with its delicate scent. Other uncommon species include the meadow thistle, dyer's greenweed, common butterwort and broad-leaved cottongrass.

The insectivorous common butterwort catches its prey using sticky glands found on its leaves. The trapped insect’s soft parts are then slowly digested by the plant!

The tall pale flowerheads of wild angelica can be found in the fringe of alder-dominated woodland around the mire. Patches of drier ground within the woodland are picked out by beech trees and sanicle. Birds that use the reserve include woodpeckers, nuthatch, siskin, redpoll and woodcock. The site is rich in invertebrates, including the dark bush-cricket and rare spiders. 


Wet and boggy throughout the year. There is a short stretch of boardwalk at the entrance to the site.


This reserve is difficult to find, and we advise that you research your route on an Ordnance Survey map prior to visiting this reserve.

From Cwmbran town centre (the Sainsbury’s roundabout), go south along the A4051, Cwmbran Drive, towards Newport. At the 2nd roundabout, take the 3rd exit right, onto Hollybush Way. At the next roundabout turn left to continue along Hollybush Way. At the next roundabout turn left onto Henllys Way. After about 1km, take a left turn into Henllys Lane (look for the sign to Henllys Village Nursery) and after 200 metres, take another left turn. Drive past the entrance to Pen-y-Werlod Farm, go 150 metres up the hill and turn left up a steep sunken lane. Drive for 1km along this lane, through the yard of Pensarn Farm and then down a hill to the end of the tarmac. Follow the road around to the right around a hairpin bend over the brow to Pandy Mawr Farm. Park on the left on rough ground just before the farm (grid ref: ST 263 926). Walk through the metal field gate and follow the green signs along the field edge. Once through second gate, turn left down the slope towards the block of alders which fringe the reserve.

Nearby reserves

Branches Fork MeadowsDan-y-Graig and Coed Meyric Moel.

What to see around the reserve

The hills of the South Wales coalfield rise behind Cwmbran. They are rich in archaeology, from remains of recent coal mining and iron scouring, to the ruins of the Celtic chapel of Llanderfal and the Iron Age hill fort of Twmbarlwm, which offers a good panorama of the Severn Estuary. Footpaths around the reserve link with the surrounding countryside.

Nearby nature reserves

Coed Meyric Moel
1 miles - Gwent Wildlife Trust
2 miles - Gwent Wildlife Trust
Allt-yr-Yn Local Nature Reserve
3 miles - Gwent Wildlife Trust

Nature reserve map

Reserve information

Map reference
ST 263 926
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Opening Times
Open at all times
1.00 hectares
Site of Special Scientific Interest (SSSI)
Living Landscape schemes
Eastern Valleys Living Landscape

There is a marked trail across the adjacent farmland from the car park to the reserve entrance where there is a short section of boardwalk. Conditions are very wet and boggy. Contact the Trust for disabled access information
Walking information
There is a marked trail across the adjacent farmland from the car park to the reserve entrance where there is a short section of boardwalk. Conditions are very wet and boggy
Limited parking off site at the adjacent farm.
Dogs allowed
Grazing animals
Reserve manager
Gwent Wildlife Trust Office
Tel: 01495 307525