With the most spectacular variation in the coastal edges in Pembrokeshire, there is a unique combination of wild plants and flowers along the extreme edges of the shores.
Saltmarshes are formed as a flat or muddy area sheltered behind a bank of shingle or sand or else along the lowest reaches of streams or rivers just like the Gann in Dale.The moving water holds silt in suspension and where the tides meet the silt falls to the bottom. Builds up particularly if there is any barrier – then green seaweeds and eel grasses can establish themselves on muddy mounds. If the tide does not soak these for three days or more then glasswort seeds start to germinate and even in winter the stiff dead stalks help more deposition – later seablite and sea purslane can strengthen and then the sea-pinks and sea-lavendar appear.
Waves move material forward from seabed. Power dissipates at the top of the shore, forming shingle banks footed by sandy shores. Gales throw boulders on top, which grind together – as it stabilises and rotting jetsam allows – sea-kale, sea-campion and sea-beet.
Where wide, gently-sloping sandy shores allow onshore winds over 15mph to drive grains inland e.g. Tenby, Freshwater West, Whitesands and Newport.These will only survive with limited footfall. Tidewrack grows where rotting seaweeds provide humus for sea-rocket, prickly saltwaort, sea-beet and then sea-couchgrass. New sand supports marram grass.