Pruning callister
 

Hi,
planted some flowering Callister at the end of April, which have grown to over 2m high over the summer. Thats 0.5 meters more then the tag informed, so how would I go about pruning it. Think the window for such action has already passed as the buds for next years flowers have already formed and really would not like to sacrifice next years bloom. Although the plants look a little gangly and need attention.

Thanks

Darren