This is Campanulastrum americanum, also known as American bellflower, and Tall bellflower. These beautiful blue violet flowers can reach 5 feet high and can live in the sun or shade. This annual plant is very beneficial to the bees, butterflies and other nectar gatherers. It is also a favorite of the hummingbirds. This flower can be grown as an annual anywhere, and it is a biennial in USDA Hardiness Zones 3 to 8.