Kansas,
United States 
when is the best time to trim back
Asked from the GoYpedia
clematis plants page
12 Sep, 2010
Answers
Clematis all have different pruning regimes, depending on the variety, and some shouldn't be pruned at all, so, if you want specific advice for yours, we'd need to know the proper name.
13 Sep, 2010
Suggest if you know the name of your clematis that you google the name+pruning Guest.
13 Sep, 2010