| Site of Special Scientific Interest | |
 Penninnis Head with lighthouse | |
  Location within Isles of Scilly | |
| Location | Cornwall |
|---|---|
| Grid reference | SV911094 |
| Coordinates | 49°54′19″N6°18′10″W / 49.9053°N 6.3029°W /49.9053; -6.3029 |
| Interest | Biological and Geological |
| Area | 16.1 hectares (0.161 km2; 0.0622 sq mi) |
| Notification | 1971 (1971) |
| Natural England website | |
Peninnis Head (Cornish:Penn Enys, meaningisland head) is the southernmost point ofSt Mary's,Isles of Scilly.[1] The headland is within the Isles of ScillyArea of Outstanding Natural Beauty and part of theHeritage Coast. It is also aGeological Conservation Review site for itsQuaternarygeomorphology and was first designated aSite of Special Scientific Interest (SSSI) in 1971 for both its biological and geological interests.[2] All of the land designated asPeninnis Head SSSI is owned by theDuchy of Cornwall.[3] On the tip of the headland is a squatlighthouse built in 1911 byTrinity House as a replacement for the 17th century lighthouse onSt Agnes.[4]
TheGilstone, a prominent rock off the eastern side of Peninnis Head, should not be confused with a rock of the same name in theWestern Rocks.
The headland is composed of coarse–grainedHercynian granite which hasweathered to form cairns and natural sculptures with names such as the Pulpit Rock. In placeshead deposits have accumulated and thinpodzolic soils have formed over the granite which is ideal for the formation of waved maritime heath vegetation. Peninnis Head is a Geological Conservation Review site because of the lack ofglacial features which makes it possible to compare with sites, such as onTresco in the north of the islands, where the granite has had some contact with glacial ice.[2]
Western gorse (Ulex gallii), heather (Calluna vulgaris) and bell heather (Erica cinerea) are the main components of the waved maritime heath and on the deeper soils bracken (Pteridium aquilinum), European gorse (U. europaeus), bramble (Rubus fruticosus) and honeysuckle (Lonicera periclymenum) are encroaching and devaluing the vegetation which is why the condition of the SSSI is considered to be unfavourable recovering. Grazing under a HLS agreement should help the vegetation to recover.[5] Two unusual plants (for the Isles of Scilly) in the species–rich maritime grassland are spring squill (Scilla verna) and thyme (Thymus polytrichus).[4] The dominant species are red fescue (Festuca rubra), Yorkshire fog (Holcus lanatus), thrift (Armeria maritima), sea beet (Beta vulgaris subsp.maritima), common sorrel (Rumex acetosa), common scurvygrass (Cochlearia officinalis) and buck's–horn plantain (Plantago coronopus). The nationally scarce early meadowgrass (Poa infirma) and western clover (Trifolium occidentale) also occur.[2][6]
Lichens
The headland is exposed to salt–laden winds and sea spray, and a number oflichens grow at the extreme tip. They include the common sea ivory (Ramalina siliquosa), the nationally scarceRoccella fuciformis,R. phycopsis, and golden hair-lichen (Teloschistes flavicans); and theBAP species ciliate strap-lichen (Heterodermia leucomela).[4]
During theSecond World War (1939–45) aRadio Direction Finding Station (RDF) was built on Peninnis Head. The first hostile enemy action in the islands occurred on 21 August 1940 when aircraft bombed the RDF. The installation was attacked on several occasions and was destroyed just over a year after the first attack.[7]
Peninnis Lighthouse was built in 1911 to replace thelighthouse in the centre of the island of St Agnes, which had been in operation since 1680. The light helps vessels to enterHugh Town harbour via St Mary's Sound. Originally powered by acetylene (provided from tanks in the adjacent one-storey building) it was electrified in 1992.[8]
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