I prune mine any time between hard freeze and when the buds begin swelling in spring. I prune to 2-3 pairs of buds.

Thanks for the reminder on those I haven’t yet pruned. It is time.

Thank you both so much. It was a prolific bloomer last year and I didn't want to mess it up. It is on a trellis, up near the house.

I would be inclined to prune that particular clematis, sweet autumn clematis, AKA Clematis terniflora, right after bloom. If the seeds ripen it can be a pest that needs weeding out of gardens or can even spread into wild areas. If you hard prune immediately after it is done blooming, the seeds don’t have time to ripen.

It is a large plant when mature, so you want to plan for a larger trellis than you currently have. Do a web search for sweet autumn clematis for some images of how large it can get. Clematis on the web says it can get to 8 meters which is something over 25’. That is even with annual pruning to the ground. It may not get that big for you, but it is a large plant.

So it's too late to prune it now? I know it can get very big and I could put a bigger trellis there but I will have to cut it back. So....to prune or not to prune, that is the question.

Prune now. I meant in future years, prune right after bloom ends so seed doesn’t form.

Agree with Babs. This is a very aggressively growing vine, both in size (huge) and in its ability to set seed easily and spread where unwanted. Cutting back lightly after the flowers finish in early fall is strongly recommended. In my climate, I would cut back hard in fall as described previously but I have no idea how well that method would work in colder climates or if it would leave the plant vulnerable in winter.

I should also say that I have grown this vine myself for a good many years and have never followed the late fall cutting back. But it shows no sign of setting seed or spreading invasively in my climate, likely because neither our summers or falls are warm enough to allow for seed ripening.

Thank you both. It is supposed to stay chilly until mid-April they just said tonight but I have seen a little bit of green starting up out of the ground at the base of this bush!! It feels like we are about a month behind this year. :(

Well, I took your advice and pruned the clematis back and am now being rewarded with lots of new growth!! So thank you so much for your help. I really appreciate it.