Tradescantia virginiana (Spiderwort)
This native wildflower has dark green, bladelike leaves and blue/purple, three-petaled flowers. You can tell the time by their blooms that open when the sun hits them in the mornings and when they close in the afternoon. The clump-forming plants will reseed, and if you have more than one variety of Spiderwort growing close together, you can get some interesting color combinations. Spiderwort grows from one to two feet in sun/partial shade and moist soil in Zones 6-8.