Area: 49.3 hectares.
In Cornwall Area of Outstanding Natural Beauty. Largely owned by National Trust.
Description and Reasons for Notification:
Treen Cliff is located on the South Cornwall coast some 10 kilometres southwest of Penzance. The site extends for around 1.5 kilometres from Porthcurno Beach in the west to Penberth Cove in the east.
Several rare plant species including one Red Data Book* plant species, the western clover Trifolium occidentale occur on Treen Cliff. The site is also of particular importance for its maritime heathland.
The mainly acidic brown earth soils are underlain by coarsely crystalline Armorican granite. This is cut by a large felsite dyke, exposed on Treen Cliff. The granite has weathered along widely spaced joint planes producing columnar cliffs, with tors and boulders on the slopes above.
The main habitats are maritime heathland and grassland, heathland, scrub, flushes and deciduous woodland. Maritime heathland is dominated by heather Calluna vulgaris, bell heather Erica cinerea, and western gorse Ulex gallii. Maritime grassland occurs on the steeper cliff slopes and is dominated by red fescue Festuca rubra, with spring squill Scilla verna, wild carrot Daucus carota, kidney vetch Anthyllis vulneraria and sea plantain Plantago maritima. The nationally rare hare’s foot clover Trifolium arvense and western clover Trifolium occidentale also grow here, as well as the hairy bird’s-foot-trefoil Lotus subbiflorus, which is largely confined in Britain to the south-west coasts and bird’s- foot fenugreek Trifolium ornithopodioides.
Scrub, dominated by gorse Ulex europaeus and blackthorn Prunus spinosa, covers large areas providing an important habitat for invertebrate and bird species. The gorse is parasitized by common dodder Cuscuta epithymum. A small area of woodland has developed on abandoned horticultural plots, dominated by elm Ulmus glabra and sycamore Acer pseudoplatanus. A number of wet flushes occur along the coast dominated by common reed Phragmites australis.
A nationally rare weevil Anthonomus rufus occurs on the cliffs. This species has been found in only one other Cornish site.
* The British Red Data Book lists vulnerable and endangered species.