The carpathian bellflowers will flower fairly continuously, from early July till Aug/Sept....as long as you continue to deadhead. The Birch hybrid has C.portenschlagiana in its lineage and will flower earlier than the Blue Clips. After blooming, you can shear back the straggly growth for another blooming in September (a bit of liquid fertiliser helps to pump out more flowering growth). Birch hybrid tends to be much smaller, only reaching around 6inches, whereas the Carpathian campanula will make a 1foot high and wide cushion. Birch Hybrid tends to have a much deeper and more saturated blue - the carpathians tend to be slightly more pastel in colour.
As you may have guessed, Campanulas have always been a favourite for me, although I favour the taller perennials such as C.persicifolia, C,trachelium and C.latiloba.
An easy and cheerful genus.

Thank you so much! Would you say Blue Clips would make a better ground cover? I am also planning to use it at the edge of beds. Or what about Pearl Deep Blue? I have thrown that one into the consideration pool.

The blue clips will tend to stay in a neat mound whereas BH (or C.portenschlagiana for that matter) will spread around (not invasively, unlike C.pocharskyana). The smaller bellflowers are terrific wall plants, growing in crevices, cracks between stair risers, tops of walls.
Not familiar with Pearl Deep Blue. The darkest blue campanula I grow is the little C.pulla - nodding dark blue thimbles, a lovely little plant.
Have fun, they are generally very rewarding, needing little more than a haircut between bloom cycles.

Thank you so very much! I trust you as the expert. =]

It's a tough decision, but I have a feeling I will fall in love with bellflowers. So I imagine there will be more orders in the future, giving me ample opportunity to explore the many varieties!

Thank you so very much! I trust you as the expert. =]

It's a tough decision, but I have a feeling I will fall in love with bellflowers. So I imagine there will be more orders in the future, giving me ample opportunity to explore the many varieties!