Bellflowers number around 300 species, found across the northern hemisphere, ranging from smaller alpine-like ground cover, C. poscharskyana to stately border perennials, C. latifolia var. macrantha 'Alba'. There won't be many gardens without a Campanula of some sort, being a staple of a cottage garden style, a typical border, with some forms happy in shade. Bell-shaped flowers, ranging from white through to lilac-purple, are on show generally during late spring into summer. The Chelsea chop can help reduce the need for staking for taller varieties and cut down after flowering to encourage a second flush of flowers.
The flowers of Campanula, whether bell-shaped or star-like, are very attractive to bumblebees and leaf-cutter bees in particular; those with a long flowering season are especially valuable. There are several native species, and many garden ones have become established in the wild. Most of these are in broadly urban locations, although C. poscharskyana seems to be spreading more widely and is therefore of some conservation concern, perhaps a risk to populations of native rock plants.