Karensusan63's Garden
Mountain Sandwort
Genus: Arenaria.
Species: Arenaria montana.
Arenaria can be annuals or usually mat-forming, evergreen or herbaceous perennials with small leaves and 5-petalled white flowers
A. montana is a low evergreen perennial forming a loose mat to 30cm in width, of small, rich green, elliptic leaves, with erect stems to 10cm in height, each carrying a few pure white flowers 1.5-2cm in width in early summer.
Cut it back after flowering if it gets over grown.