I'm not aware of how hardy this particular variety is ... though, to be on the safe side, I'd wait until the ground is pretty much about to freeze and then hill it up well with dry peat moss or even just garden soil. Shovel snow upon it as soon as it arrives and hopefully before bitter cold has set in. Leave the trimming to spring when you can see just how much live wood has made it through.

I've seen varieties such as 'Limelight' with varying amounts of winter dieback and it still blooms well on new wood.

Technically speaking your to cut them back in the spring. Two buds from the ground. I like to cut them back in the fall because I'm in Ontario and we get fairly mild winters.

But, the only probelm with cutting them back in the fall is if you get a severe winter the plant will suffer dieback and you way lose the plant.

In your region i would cut back 1/3 of the top growth, in the fall. Just to clean up the plant. Then wait until spring to do a severe pruning.