As soon as you plant your crepe myrtle, it will start straightening as it grows. The light will come at it from all different directions unlike in the nursery. When you plant it, plant it as straight as possible and let the plant figure it out with new growth.
Original article: https://www.reviewjournal.com/life/home-and-garden/curved-trunk-of-crepe-myrtle-will-straighten-out-as-it-grows-2742489/
