There are two native species of spiderwort, Tradescantia virginiana and Tradescantia ohiensis.  While there are different colors--blues and purples--that isn't really the way to distinguish the species--it has to do with how hairy certain parts of the plants are.  We probably have both species, plus possibly some cultivars that have escaped from gardens. The video above includes some fun facts about spiderwort, which is common along the trail in May and June. 

Besides spiderwort, there is a related plant called Asian dayflower, or sometimes Flower-of-the-hour because like most of its relatives, flowers only bloom for a short time in the morning.  This species is much less spectacular than spiderwort. Its Latin name is Commelina communis, and as the common name tells you, it isn't a native.  The clear blue of the flowers is unusual, which may be why gardeners chose to grow it.  It's an annual that may be quite spready, but generally only in moist places where there isn't a lot of competition from taller things.