It all depends on the variety. Some leaf out earlier than others. Be patient.
This sounds like you have one of the grafted crepe myrtles. Most are not grafted but some are. Just hope it is a desirable rootstock.
Some CM were grafted, that is, a different type of CM than the roots, were attached to the roots. This is done to make a stronger healthier end product tree. After the rootstock is the correct size the grower can attach a scion (cutting) to the rootstock that is the desired color and will be the desired height. It is akin to citrus trees where sour orange or trifoliate roots are attached (grafted) onto lemons, oranges or just about any citrus tree. The sour orange or trifoliate is a terrible fruit tree but when the roots are grafted onto an orange scion it makes a wonderful fruit tree.
Most CM's are hybrids. That is they grow on their own roots, but since your tree died and the roots lived it is grafted.. What I can guarantee is that the grown tree will not be anything like what you expect. How did you determine that the trunk was in fact dead?Interesting. Good info. I knew fruit and nuts trees were but not CM. Hopefully mine was grafted to be perfect.
There is no way to tell except to ask the nursery the name of the rootstock and they may or may not know it. Then ask who the grower was and ask him. But I can say this, most rootstocks make terrible specimens.
