Campanula are one of the hardiest and adaptable perennial thrillers. Campanula Blue Water fall cascading down a wall or over a planted container of mixed delights puts on quite a show from late may to Julys heat. 8-10 inches tall. the dark blue flowers are bells that avalanche down.
Campanula Birch Hybrid starts its blooming frenzy june into september. It is 8-10 inches high mound with blue bell flowers. This is a good front, lightly shaded, planting bed. removing the spent flowers will encourage more blooming.
Campanula glomerata Freya is an upright type of campanula.It doesnot form the mat appearance the others do, but has an upright blooming habit over top a mound of green foliage. It has clusters of deep blue flowers forming blue globes along the flowering stems. about 15 inches high with a dense 12 or so clusters of flowering stalks.
This would make a great potted plant as well as a good middle height area of a perennial border. ( do people actually plant perennial borders any more?)
consider using Campanula in a mixed patio container.