Mountain Sandwort is a mat-forming perennial from the mountains of Spain and Portugal, producing a low, spreading cushion of fine foliage covered in masses of small, pure white flowers in late spring. The effect at peak flowering is of a white-frosted mat - the flowers are so numerous that the foliage is largely hidden. It suits well-drained, rocky positions and is one of the better white-flowering groundcovers for dry sunny situations. Full sun. Excellent drainage. Drought tolerant once established.