Clusterhead Bellflower (Campanula glomerata 'Joan Eliot') has handsome blooms, typically bell-shaped, blue flowers from spring to fall. It should be planted in sweeping drifts in the perennial border or naturalized under trees. It takes sun/part shade. It reaches a height of 18" and can be invasive. During its blooming period (May-June) in Maine, it is spectacular; however, the rest of the year, it is undistinguished. I noticed the blooms this week. Wow!