Answer: Yes, they will grow in northern New Jersey but may be killed to the ground during harsh winters. (The roots are hardy, however.) For this reason they will probably not reach the tree like proportions often seen in the southern states. They will however bloom quite nicely in late summer because they bloom on new wood produced each season. The best way to try to protect these is to plant them in a warm and sheltered spot out of wind and to be sure they are in well drained soil. They will be least hardy for the first year or two until they become well established. Northern New Jersey is primarily in zone 6, but areas close to the coast are in zone 7. The Bergen area would probably contain many microclimates between the two.
Wake County in NC, by Raleigh, is much warmer -- running on the edge between zones 7 and 8 by microclimate.
Good luck with your crepe myrtle!
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