I’ve tried growing several varieties of Campanula (aka bellflower) the last two years with little success. Most of them don’t seem to make it past the summer in my garden. My mistake was probably planting them in full sun and allowing the soil to dry out between watering, as Campanulas seem to need consistently moist soil. On the other hand, my Campanula persicifolia was planted in a spot where it did receive afternoon shade, but it got crown rot last summer. Fortunately, the persicifolia produced a few side shoots, which I was able to save. These survived the past winter and, having learned my lesson — to keep the mulch away from the base of the plants — I’m looking forward to seeing them bloom this year.
(Note: I just checked the Missouri Botanical Garden website, and they confirm that Campanulas should be protected from afternoon sunlight in zone 6 and need consistently damp soil. Wish I knew this before I bought all those bellflowers!)
Last year I also planted two varieties of Campanula lactiflora — ‘Prichards Variety’ and a seed-grown strain from Far Reaches Farm, called NCE219 — but it’s still too soon to tell if they survived the winter.
All my other Campanulas were planted along a flagstone walkway. Because they all seem to struggle in this location, I might just replace them all with Veronicas, which have been growing very well for me in the same sunny, dry conditions along the walkway. In the photo below is Campanula ‘Blue Orb,’ from Bluestone Perennials. I completely underestimated the size of this plant, which easily reaches 8-10 inches tall in bloom. I planted two of them in between the flagstones, expecting them to form tiny little mounds.