Answer: You can deadhead meaning cut off the faded blooms, this can help keep it blooming later in the season. Do not prune it back however as this will stimulate late season growth that will not harden before winter and this can cause excess winter cold damage to the plant. Also do not fertilize it for the same reason. I should point out that this plant is considered root hardy into zone 5 but you are in zone 5A, the coldest part of that zone. Since you are planting in the fall rather than spring, there is a greater risk of winter loss with this plant as it will not have had all summer to become rooted and established. (Also, depending on your microclimate you may actually be gardening in the equivalent of a zone 4 location.) For these reasons I would suggest you give it winter wind protection as well as using a very deep mulch, apply the mulch in late fall after freezing weather. In spring be very patient waiting for it to come back into growth. You will need to prune it in the spring to remove winter killed branches, wait until late spring to prune as the branches provide it a little bit of winter protection. Good luck wiht your butterfly bush!
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