Pretty much any :-)) 6 hours of direct sun is considered a full sun situation, regardless of the time of day the plant receives it. FYI, bicolored or bright pink clems generally hold their color better in part shade. The more strongly colored blooms (deeper 'reds', blues and purples) need the sun to develop their intense coloring and hold up well. Whites, IME, will tolerate any light situation.

I have not had much success growing clematis in z2b with 3-4 hrs sun max. Let me know if anyone has done well in similar conditions or if I am just dreaming!

Thanks,

Annie1

Annie, you may be pushing the outer limits of hardiness for most clems. Generally, zone 3 is the quoted lower limit but certain species may survive that. Articles have been written on the ability of the large flowered hybrids to thrive and bloom in that extreme a climate (specifically, Calagary, Alberta) and the consensus is that while they may survive, blooming ability may be seriously compromised. Certainly any group 2's would be at risk, as they would likely experience a complete dieback during winter of any top growth. Those that bloom on new wood (group 3's or any hard prunes) may produce better results. Another consideration would be the shortness of your growing season and the lack of intensity of the sunlight that far north. Even though my growing season is much longer, my rather northerly location (Latitude 47) does not allow for much summer heat or intense sunlight and the bloom season for many clems even here is later than more southerly, but colder zones.