National Grid Reference: SH599809, SH603810

Site Area: 7.54 ha


This site is of special interest for its heathland and grassland communities as well as for its vascular plants. It occupies a south facing escarpment on Carboniferous Limestone which forms a prominent feature in the landscape of south-east Anglesey, 5 km north of Beaumaris, and encompasses a small disused quarry.

Mariandyrys supports a rare example of heather Calluna vulgaris - western gorse Ulex gallii heath of the salad burnet Sanguisorba minor sub-community. This unusual vegetation comprises a mixture of both acid and lime tolerant plants in close association, often as a complex mosaic with tussocks of low ericaceous shrubs such as heather, bell heather Erica cinerea or western gorse interspersed with such lime loving plants as the common rockrose Helianthemum nummularium and thyme Thymus praecox. This mix of calcicole (lime loving) and calcifuge (lime hating) plants appears to be related to thin deposits of drift or wind blown silt (loess) partially masking the underlying limestone rock, but the balance is a delicate one in which management by grazing and burning has also played a role.

The heath is accompanied by a small area of sheep's fescue Festuca ovina - meadow oat-grass Avenula pratensis grassland of the Dicranum scoparium subcommunity and patches of sheep's fescue Festuca ovina - carline thistle Carlina vulgaris grassland of the crested hair-grass Koeleria macrantha subcommunity. Associated species include quaking grass Briza media, glaucous sedge Carex flacca and spring squill Scilla verna. Fringing areas of scrub provide sheltered conditions for grazing stock and nest sites for birds.

This is the main site in Anglesey for the nationally scarce spring cinquefoil Potentilla tabernaemontani which occurs alongside populations of wild onion Allium vineale, columbine Aquilegia vulgaris, mountain everlasting Antennaria dioica, small scabious Scabiosa columbaria, fragrant orchid Gymnadenia conopsea, autumn lady's-tresses Spiranthes spiralis and pale flax Linum bienne. The site also supports a diverse range of invertebrates including molluscs and a number of uncommon insects such as the weevil Otiorhynchus desertus, Ashworth's rustic moth Xestia ashworthii and the fly Cnemacantha muscaria .


Part of the site is managed as a nature reserve by the North Wales Wildilfe Trust. This part is also a registered common.