This is an amazing perennial because it grows in a green mat 12"-18" tall in virtually any sun/part shade/ full shade condition. It has spiked purple flowers that appear in late summer and dark green foliage. It is great as a ground cover, virtually indestructible. Now that I have told you about it you will see it everywhere...(that is the only downside actually). It's a fairly common plant, especially in cities. But I used it recently as a ground cover with Crepe Myrtles in a project on LI and it is a very distinctive combination.
Conditions: Full Sun to Partial Shade