I think the cold we had in early Feb. killed the tops, but I would give it more time. Mine are all shooting from the bottom. It is still early so I am waiting a bit before cutting off the dead looking parts. Sometimes crepe myrtle is very late shooting out and this is strange weather we are having this spring. I have damage on other trees and shrubs that are normally hardy.

I think you should wait awhile too. I doubt the tops are completely dead. I've seen the tops leaf out later than the new growth at the bottom before. Mine are doing the same thing as yours, new growth at the bottom and nothing on the top yet. I don't think it's uncommon for crape myrtles to do that.

One of my Crape Myrtles, Acoma, has sort of a tree form but it's hardier than my standard crape myrtles, which have LOTS of trunks coming up from the bottom. I don't think those could ever be "trees" no matter how much pruning a person did. I gave up a long time ago and just let them be shrubs. It shouldn't hurt them to thin them out. It's just a lot of work and you might have to repeat every year. I wonder if our colder weather makes them tend to be bushier.

Over several years, I have trained my "forest" along the driveway to tree shape. And I have thinned some out, but there are still too many. This year I have been pulling the new bottom growth away and off from the trunks, rather than cutting them. I've found the new bottom growth doesn't come back nearly as much that way.
Wonder if this isn't a "message" to me that it's time to just get them out, since a few of them are 15 ft. tall.

One great thing -- this should delay our annual Japanese Beetle problem!
Sunny

Thanks everyone. I think I will start thinning out some, but wait a little longer to cut the tops off as I do have one that has some leaves now on 3 of it's upper trunks. The other two have nothing but the bottom shoots so far. I had a lot of dead areas on my knock out roses that had to be cut out so I do think that bad cold spell did some damage.

I asked the man who runs the Botany Shop and he said to wait a while. I have already cut off my Knock Out Roses. They were dead above the snow line also the same for dwarf deutzia. My pink dogwood, Oak leaf hydrangea are not shooting out normally. A Japanese Maple is shooting out below the snow line and several viburnums are shooting out at the bottom. Nandina is dead on top and all crepe myrtles are coming up from the bottom.