Sea Rocket (Cakile maritima) is one of the first colonisers of loose sand at the top of the beach on the strandline left by the highest tides. It is a member of the cabbage family (Brassicaceae) with very pale lilac 4-petalled flowers – sometimes pink or even violet. The roots begin to bind the grains together to stop the sand from shifting. And that is the beginning of fixed dune formation and provides the conditions for other plants to settle.
Jessica's Nature Blog 