I am trying to identify a perennial that I put in my garden a few years ago.  It grows in a clump and doesn't spread.  the leaves are a deep green with small serrated edges.  The leaves at full growth are 3/4" wide by 1" long and each branch grows in a cluster.  Each plant is approximately 1+ foot in diameter.  It produces flowers  in June that pass quickly.  The flowers are lavender and are flat with 4 or 5 petals.