Mulch in the winter. Sounds like the location is as close to ideal to try 'zone pushing'. I would say you have a reasonable chance of it making it through.

I bought one this spring too. I've seen it listed as anything from zone 5 to zone 7. It's a new variety so I don't think anyone knows for sure yet. I bought it because it is a close relative of Blue Fortune Agastache which is hardy to zone 5. These are supposed to do better if they don't get wet in the winter and have a rock mulch. Let's hope both our plants do well.

I have a few zone 6 and zone 7 plants. Usually I cover them with as much snow as possible in winter. It is not only the cold that kills them though, many times they rot in the ground from our wet fall and spring.

I don't know if this will work but I've read about them doing it to bushes in the far NE states like Vermont and New Hamshire. Find some way to wrap loosely wrap burlap around it and stuff the inside with straw or leaves. I did the same thing as you, except mine is a clematis Montana Rubens. It was sold at Menards and the tag said that is was hardy to zone 4 but after doing some reading I have found out that it may survive the winter up here but the foliage will almost completely die back to the ground so I never get any flowers! It only blooms on old wood. I am going to try the burlap thing myself this winter so I thought I'd mention it. I really hope it works.

Kimberly