Answer: Your zip code places you in zone 5A, the coldest part of zone 5. This may actually be as cold as zone 4 depending on the microclimate where you garden. So, although butterfly bushes are winter hardy into zone 5, they may not survive your winters. The best you can do is mulch heavily in late fall. Do not prune until spring. The reason to wait is that the branches can help provide a little extra winter protection. In the spring trim off any winter killed branches, if necessary going all the way to the ground. Then be patient and see if they resprout. They bloom on new growth of the season so should still bloom for you assuming they survive the winter. Good luck!
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