It's one of the late flowering clematis, so its prune group 3, which means it should be cut down in midwinter to about 8-10 inches from the ground. Further info in the link below

https://www.rhs.org.uk/Plants/50038/i-Clematis-i-Star-of-India-(LL)/Details

Thank you Bamboo! Much appreciated.

I have a wild clematis called 'Sweet Autumn". It found me, I had nothing to do with it. I could swear it keeps trying to strangle me whenever I walk by.

:)
Plants and flowers which appear freely are a nice thing!