Oyster plant or Beach bluebell.  M. maritima in the borage family is a spreading, prostrate perennial with fleshy, blue-grey-green leaves, up to 10cm long, and branched clusters of bright blue, bell-shaped flowers opening from pink buds in early summer. It grows on the beach, but in colder areas of Canada, Greenland and Svalbard. Sun or part shade will evidently grow in clay soils and obviously free draining ones that don't dry out too much. I am trying it in a sand bed and in a cooler position, brilliantly so far. Edible leaves tasting like... you guessed it oysters!  Photos from wikipedia showing pant in its natural habitat.