Q.campanula blossoms do not open
I have several clusters of campanulas with lots of blossoms on each; however, the blossoms stay as puffy little balloons rather than open to reveal the inside. I have to go around and open them each individually. The blossoms will stay in the puffy state up through the end of each blossom’s cycle.

Downtoearthdigs
Answered on July 15, 2015
Most likely an environmental issue. It's just not happy with the temperatures.
They will likely open on their own eventually.
https://www.gardeningknowhow.com/ornamental/flowers/campanula/growing-campanula-bellflowers.htm
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