Sisyrinchium angustifolium (stout blue-eyed grass)

Despite the grass-like leaves, this is actually in the Iris family.  Small blue-violet flowers appear in late spring to early summer. Naturally occurs along woodland edges and in oak savannas. At about 6 inches tall, it's a good choice for the front of the garden or the edge of pathways.  

Photo 1: Melissa McMasters / CC BY 2.0

Photo 3: Fritz Flohr Reynolds / CC BY-SA 2.0