Considering its a clematis suitable for winter zones as well as the warmer ones and can expect to be hit by snow, I cant see why it cant be cut back --at least somewhat--to prevent heavy snow bringing it down. So, go ahead cut it back as you wish as long as you feel lthe plant has hardened off for winter. But as you said its still has buds and last remnants of flowers, I'd wait until after a hard frost before cutting it back.

Sweet Autumn Clematis is an invasive vine--seeds all over the place here.

That is a fabby pic! I imagine that clematis has a few years on it- like 5? Mine sweet autmn is in it's third year and it is already budding leaves at the TOP of my porch. Yes I opted not to cut it as I need the height now. You swear those skiny vines are dead- until the leaves pop out! I'm not bad mouthin' sweet autmn is it a fine choice- but not your only choice. jlink, You may also want to consider clematis tangutica which grows like a son of a gun and has yellow penant blooms and the cutest seed whorls after. If you want more leaves and a more solid than whispy look also consider the variagated porcelain berry vine. 'ampelopsis elegans' It is in the grape family and does get some teeth marks from jap. beetles. It is not invasive like the plain green. In fact mine isn't invasive at all! It will also get height in a hurry esp. after it's second year. Karen

Any clematis can be used as a groundcover. Generally speaking, clematis do better if they are climbing over something as they can be prone to being eaten by earwigs and other nasties that like living under them. Might not be an issue with the hot humid climates that you garden in. You might also want to consider Jouinana praecox as a ground cover. I have it growing on the ground and through a tree shaped variegated ligustrum and it has not seemed to be bothered by the usual bugs that like to chomp on clematis leaves and flowers. Sure isn't as invasive either. The stems will root if the area they are in is mulched and there is some ground moisture. My pictures don't do just to the flowers and their color so have linked you to its listing on the Brushwood Nursery site for it below my pictures. Here is a link that might be useful: Brushwood Nursery Listing