I know when to prune these things. The real question is how? In what manner? To what extent? I have two crimson specimens that refuse to bloom! I will give them one more season to produce. If they fail to do so, out they go!! I live in eastern Pa and the Crepe Myrtles do magnificently here, except mine!
Pruning Crepe Myrtle
Certified GKH Gardening Expert
This article should help you with that:
And you may want to read this one as well: