Arabis

Arabis, or "rock cress", as you can guess from the name, is one of those plants that like tough love - give it a hot, dry crack between some stones somewhere and it will flourish. It can cover a stacked-stone wall or rocky outcropping with beautiful flowers. They make attractive low mounds that look great at the edge of retaining wall where they get full sun and excellent drainage. Cut stems back after spring bloom to keep plants compact.