Here in zone 6A we have to prune crapemyrtles back annually. Two or three years ago they had actually started to grow because of an extended early warm spell when we got a 20° freeze. They went to the ground. If the winter has normal moisture and temperatures all that is required is to cut off the spent seed capsules. If it has been very cold and dry, they will probably need to be cut further back. Having said that, in zone 8 you should have little problem with these kinds of winterkill. I don't think you will have "crape murder!"
hortster

Hmmmm. Are you saying that the nursery has already topped the trees? That sort of pruning is not 'fixable', but perhaps that's not what they did. Can you let us see a picture of one of the victims? I don't like the words: "cut back" when it comes to crapemyrtles, I have to admit.

Are you ordering these plants sight unseen? I feel very strongly that crapemyrtles should never be purchased that way. So much of their beauty, in my opinion, is created by a unique structure....what I call 'good bones'. You should hand pick the ones you think will grow up to be beauties. They should be a structural showpiece in the winter, too.

Crapemyrtles do not need to be pruned at all. Removing their seed pods is a waste of time as the new growth will grow around the flower stems come spring. The pods and flower stems will simply fall off. Some simple detail pruning (crossing branches, inward growing branches, and similar) should be done only to enhance the physical beauty of this tree.

What kind(s) are you ordering?

I guess that I was unclear in my message in the first post. My intent was to say that, even if cut back severely, crapemyrtles are tough and will normally recover. In zones 7A and 8 crapemyrtles are at home and become trees. Here, in 6A, considered large shrubs, they are often zapped by the wild variances in winter weather and require heavy pruning. rhizo is completely correct in stating that they require no pruning as the new growth will cover the old flowering tips and the capsules will fall off. However, in zone 6A crapemyrtles don't begin new growth for the season until nearly June 1, when all else around them is in full, fresh new growth. Trimming the spent capsules off at least gives them a freshened look until they take off again for the new growing season. Any crapemyrtles that have been healed in at a nursery or that are coming from a more northern location, carried over for the winter, usually require a serious pruning back to green wood (here). Sorry for the confusion.
hortster

Good job, hortster. We all, myself included, need to remember to take regional climate into account when it comes to topics like this. I still think of Crapes as being a strictly Southern ornamental, but that is no longer the case.

To further clarify what hortster wrote, some varieties are not cold hardy and they die back to the ground like perennials and only need pruning if you don't want a dead stem(s) there in your garden. This is not limited to zone 6. Even zones 7 and maybe even 8 can have this problem in colder winters which is why it's important to plant proven varieties.

Topping them to promote blooms is what is meant by 'crepe murder' and this is neither needed nor recommended except by landscaping firms that charge people who don't know better to do this. Having gone through the process of hiring a new landscaper for our HOA recently, it's laughable how many boast that for a low flat fee, they will prune all your crepe myrtles. It's just a money making scheme. Somewhere along the lines homeowners have picked up the bad habit because they see butchered myrtles all over town.

Fortunately, there are now many, many CMs on the market in a variety of sizes and forms and everything in between. Some remain as shrubs ('Baton Rouge', 'Rosey Carpet', 'Velma's Royal Delight', etc) and some get to be good-sized trees ('Biloxi', 'Natchez', etc.). Depends on variety.