This past April i did just that, a hardy crepe myrtle that was 12 feet high. I
cut the entire shrub almost down to the ground, dug up its large roots, and
replanted it. It recovered very easily and bloom for me this late July and I
live north of washington...nyc. And to my suprise, the move had given me 7 more
c.m. where somehow some roots must of been left there. Wonderful color now in
the fall. So i would wait around april. good luck