Rockcress
(Arabis alpina)

This mat-forming perennial grows 4 to 10 inches tall and has white, 4-petaled flowers.  It is native to the mountains of Europe.  Rockcress is a spring bloomer that makes an excellent ground cover, and it works well in border edges and rock gardens. The fragrant flowers attract honey bees. Prefers lean, well-draining soils. Provide some afternoon shade if grown in USDA zones 7-8.  Foliage can be cut back after blooming to encourage a denser growth habit.