Date of Notification: 11 March 2011
National Grid Reference: SH555792
O.S. Maps: 1:50,000 Sheet number: 114
1:10,000 Sheet number: SH57NE
Site Area: 25.2 ha
Rhosydd Llanddona is of special interest as an example of lowland heathland. The site is in two main sections, to the west and to the north-east of Llanddona. The site overlies schists of the Gwna group which outcrop in the west of the site and lies at an altitude of approximately 130m. The western section, on the north-eastern flank of Mynydd Llwydiarth, is characterised by rocky outcrops supporting heathland with intervening areas of mire and grassland. The eastern section of the site is a relatively flat area of common land which is divided into three main blocks by minor roads.
The dry heathland is dominated by heather Calluna vulgaris, western gorse Ulex gallii and bell heather Erica cinerea, with occasional purple moor-grass Molinia caerulea. Lichens are locally abundant including Cladonia portentosa, C. chlorophae and Parmelia omphalodes. Small areas along the eastern edge of Tyn y Mynydd are more species-rich and include heath bedstraw Galium saxatile, tormentil Potentilla erecta and marsh lousewort Pedicularis palustris.
Areas of wet heath support abundant cross-leaved heath Erica tetralix, heather and western gorse, together with purple moor grass and creeping willow Salix repens. Heathland merges into mire which is dominated by purple moor-grass with frequent creeping willow and cross-leaved heath. Petty whin Genista anglica is widespread within the mire, as is bog asphodel Narthecium ossifragum. Devil’s-bit scabious Succisa pratensis, greater bird’s-foot-trefoil Lotus pedunculatus and at least six small sedge species are amongst the wide range of plants present within the mire.
A large depression in the middle of Tyn y Mynydd supports a series of mire and rush pasture communities. This area supports several less common species, such as blunt-flowered rush Juncus subnodulosus and black bog-rush Schoenus nigricans, which add to the interest of the site.
Uncommon plants present at this site include a hybrid sedge Carex x fulva at Tyn y Mynydd, pale dog-violet Viola lactea and lesser butterfly orchid Platanthera bifolia at Llaniestyn Common.
of the site is registered as common land.
Part of the site is declared a Local Nature Reserve.