Do you have Campanula persicifolia var. planiflora ‘Coerulea’ currently in stock at the nursery?
You should remove the faded blooms to encourage further flowering. You should grow them in full sun with well drained, moderately rich soil. This plant will need regular dividing as it is a very rampant grower.
Annual self-seeding, or division, or sow in spring.
Pests, diseases or disorders
Is prone to slug attack and rust may be a problem in autumn.