· Brent Wilson's Answer
· Hi Yvonne - If you pruned your 20 foot tall crape myrtle halfway back this should not kill it. A crape myrtle can be cut all the way back to a stump and will still reemerge, sending out new shoots. That being said, if you pruned it during summer this might do some serious damage to the tree. I'm not sure though because I have never done heavy pruning on a crape myrtle during summer. Any heavy pruning on crape myrtle should be done in late winter, while the tree is in dormancy.
So, if you've already cut the crape myrtle back, you'll need to wait until late next winter to do any more pruning. Rather than go into detail here I'll provide a link to an article that provides tips for standard pruning and for corrective pruning, which is necessary when a crape myrtle has been cut back too far. www.gardenality.com/Articles/344/How-To-Info/Pruning/How-To-Prune-A-Crape-Myrtle/default.html
Hope this helps. Let me know if you have any other questions,