COUNTRYSIDE COUNCIL FOR WALES
SITE OF SPECIAL SCIENTIFIC INTEREST: CITATION
ANGLESEY PORTH DIANA
National Grid Reference: SH254781
Site Area: 0.8 ha
Porth Diana is part of the nationally important coastal heath on the west coast of Holy Island. This heath, which is very exposed to westerly winds, is developed on a rocky escarpment. It is short in stature and typically consists of ling Calluna vulgaris, bell heather Erica cinerea, western gorse Ulex gallii and creeping willow Salix repens. The locally rare, dyer's greenweed Genista tinctoria occurs in its only extant Anglesey site here.
A distinctive assemblage of plants occurs on the thin soils around the bare rock areas. Annual rockrose Tuberaria guttata ssp. breweri occurs in great abundance here. Associated species include spring squill Scilla verna, English stonecrop Sedum anglicum, birdsfoot Ornithopus perpusillus heath pearlwort Sagina subulata and early hairy grass Aira praecox.
Tuberaria occurs in only eight localities in Britain, seven of the others being in Anglesey and one in the Lleyn. Of the seven Anglesey sites, six are on Holy Island. The population of Tuberaria at Porth Diana appears to be the largest of any of the sites.