The two most likely possibilities are 1. a water/drainage issue and 2. temperature shock.

You should test your soil with your finger to see when your tree needs water. When the soil about an inch below the surface just starts to dry out, it's time to water. You don't want the soil at root level to dry out. You also don't want to overwater, but that's not likely if you have well draining soil. Just check! Remember that slow, deep watering is much better than brief, shallow, frequent watering.

Other issues can be associated with water problems besides the actual quantity and frequency of water. Drainage is a key factor. Hopefully your soil has at least average drainage and you didn't amend your soil when planting the tree. Planting depth is also important. Hopefully your tree was planted so that the top root was approximately at the level of surrounding soil. It's important not to plant too deep. Another issue is drainage between rootball and surrounding soil. If your tree was potted, you'll want to check the rootball and the surrounding soil when you check for moisture levels. It's possible for the rootball to dry out before the surrounding soil or for the surrounding soil to dry out before the rootball. Either of these conditions can lead to problems.

The second possibility was temperature shock. Crape (not crepe, btw) myrtles around here have not yet leafed out. Since you said yours had, it makes me consider the possibility that it may have been grown in a greenhouse and not properly hardened off before planting. If that is the case, the sudden jolt it got when entering the real world could have made it drop some of its leaves. If this is the case, I think there's a good chance it will recover.

The only thing you can do for now is provide proper watering, mulch it correctly (if you haven't already done that), and sit back and watch to see how it does.

Here is a link that might be useful: Proper Way to Plant a Tree or Shrub

sounds like frost/freeze issues if it were in my z5 .... plus the water issue which brandon noted ...

how cold did it get in the cold snap??? any other frost damage in the yard ... besides this tree

ken

Where are you? All zone 7 areas are not equal.
The tree is probably just fine. Scratch the bark, is it green underneath? Then it's ok.
It is almost impossible to kill a crape myrtle although die back on top can happen in a new tree from sudden freezes.

Plant the tree and don't worry about it. It will resprout new leaves. In June, go out and cut back all branches that don't have leaves.

They are also, btw, one of the last trees to produce leaves in the spring.

Thanks brandon for your advice. I'm wondering if I have a drainage issue. I notice that after I have watered it for a while water begins to accumulate around the area where the tree is, almost like a puddle but then after a while it soaks into the ground. We do have a french and a soaker drain around the area of the tree because of previous drainage issues. I did go outside and looked at the tree. It looks like it is budding. It looks as though new growth is starting to appear. I'm taking this as a good sign. I guess we'll watch and see what happends. To address Ken's question, the cold front that came throught probably dropped the temperature to the low 30's. Everything else in the yard was fine though, the only other damage I saw were my neighbors plants that she had also planted the same weekend and they died from the temperature drop. Thanks again.

Yeah it looks like you bought a crape myrtle that leafed out in a warmer zone and then shipped to your zone...where you bought it. The freeze came through and then they froze off. The crape myrtles here just started leafing out last weekend, so zone 7 should be a week or two behind us.

This has happened before to our fully leafed out crape's (spring 2007), and they recovered nicely and flowered that year. They may have flowered a week or two later though due to the freeze. Since it is a new planting you may have sucker branches growing from the bottom of the trunk later in the season. Time will tell though. Good luck!