Answer: Yes it is a bit cold there for crepe myrtles to reach those tree-like proportions we enjoy further south. They may be killed back to the ground during a difficult winter, and they also tend to leaf out quite late in the spring.
In a sunny spot, you might consider Cornus kousa, a special dogwood. For sun or part shade you might consider the native redbud or perhaps a serviceberry. There are some smaller varieties of disease resistant crabapple and ornamental cherry that make lovely specimen trees, too.
A large flowering shrub that can be trained to tree form and blooms during the summer is the hardy hibiscus or Hybiscus syriacus. If you really would prefer a summer blooming plant in that location, this might be one to consider. I would look for a modern, named variety in a color you like, preferably one noted for being sterile so it will not seed itself about.
Your choice will be limited by the amount of space vs. the mature size of the plant as well as by the lighting and the kind of soil you have. Your county extension and local nursery personnel should be able to help you in making a selection that is both suited to the location as well as providing the ornamental look you are hoping for.
I hope this helps you get started in the decision making process.
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