Answer: You may have a plant that blooms on old stems and also reblooms on the new growth once it has matured. (Different clematis behave in different ways.) I would suggest you experiment and prune some each way meaning half in fall as you used to do and half in the spring as you did this time; then you should have two good bloom flushes plus some new growth from the base. Alternatively, if you have a preference for when it blooms you can prune accordingly.
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