Pruning callister

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.
Darren Moden

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.