craple myrtle, recovering.

HI, some tips where given here. The recovering process is doing good. Now, Do i need to prune it always so i can keep it flowering?

I was wondering if anybody could tell me if there are certain areas,like here in the desert Southwest,where crepe myrtles do not like to grow?I have not been able to keep one alive longer than five years at the most,as a bonsai.Nor have I ever seen many real old CM bushes in the landscape here in Albuquerque,although nurseries are full of nice specimens.Like redbuds,I have learned to leave them alone.