after googling how to, the recommendation is to trim braches that are the size of a pencil or smaller.
Our landscaper in SC said the crepe murder is done by the ones who want to charge more hence they murder the tree to show how much they have done.
We all know that if nature intended for the trees to be trimmed that way there would be a tell tale.
Some folks think it just forces new blooms because of the continual new growth.
That in my opinion is not a good excuse because we do not do crepe murder and have a beautiful health specimen.
See the attached:
http://www.southernliving.com/home-g...-crepe-myrtles