Q.dead crepe myrtle tree
We cut a root several feet from the tree when digging a trench last year. This spring the tree did not bloom but a vast amount of new growth is shooting up from the base of the tree. Will the tree (30′ or so) renew next year or should we allow the new growth to continue and hopefully create a new tree?

Certified GKH Gardening Expert
Yes, this was likely damaged when the root was cut. The old shrub will not likely recover anytime soon.
You will want to select a new cluster, or single branch to become the new shrub. Keeping this shaped will require constant pruning of the basal shoots until they stop forming. This could take a year or more.
You could also leave it to grow naturally, but it will become quite unmanageable and prone to disease if left this way.