Posting this picture, I so sorely felt the need for more collective nouns for flowers that I was forced to invent one. ‘A tumble’ was my first thought, but then I remembered that the best collective nouns are more quirky.
As they all seemed to be looking in different directions, I chose ‘an inspection’, but it could just as easily have been ‘an introspection’. You might have a better idea – if so let me know!
The colour is not true to life – too purple – but I liked the petals’ iridescence and the way light is falling.
Shared for Cee’s Flower of the Day.
Susan Rushton 
I love campanula! Ours are flowering too (SW England). Introspection is a great collective noun. I also think perhaps a “flourish” would work… But now that you have posed this question, my writing brain will be beavering away at this!!
A flourish would be great too. Or an aspiration because they seem to want to get out of their pot.
Eunice beat me to it. Alliteration as a bonus
Perhaps this is why there are so many collective nouns for the same thing. I wonder if there was a time when they were invented – a kind of literary craze?
Probably
I think “a tumble” is perfect.
These ones tumble just as far as their greenery will let them.
I love Campanulas, but they don’t love me back. They’ve never really taken to my garden. My favorite are the white peach-leaved bellflowers – C. persicifolia.
Those are nice too. They are such a varied group of plants.