Cold snap. I covered mine in 3 gallon and one still got wacked so I pruned.

Here is a link that might be useful: Propagating Perennials

We in St Louis had the same problem last year. A late frost devastated the new leaves. We were advised to do nothing. The tree would send out new leaves. It did, although not as fully as it had in previous years. This year I can see that it is still struggling from last years trials. New leaves are slowly appearing but there is much branch dieback. I spoke to the botanical garden this morning and was advised to wait until it had fully leafed out, then trim back the dead branches. Do not feed and make sure the tree has adequate watering during the summer. Patience is in order.