The Clustered Bellflower blooms briefly in June.  It has weak stems that flop over easily, and wilts terribly at the first sign of hot weather.  They range in height from 1½'-3' in my garden.  I grew mine from seed, and was surprised to get three different colors - purple, light-purple and white.  I had only expected purple.  The purple one pictured is one of the shorter, and more densely flowered bellflowers I have.  It holds its stems more upright than my other purple ones.  They have suffered winter kill the last two winters.  I only have one plant left, and it's probably a purple one.