Answer: In my experience Clematis really needs ample direct sun to bloom well, preferably all day or at least a half a day. In just a few hours of late afternoon sun I would probably suggest the sweet autumn clematis (Clematis paniculata) as being among the more shade tolerant, it has white flowers that are very fragrant and blooms for quite a long period in the late summer to fall. I would expect the bloom quantity to be relatively lighter than it would be in more sun however. Another long blooming white flowered and more shade tolerant plant you might consider is the climbing hydrangea, Hydrangea petiolaris. Your local county extension or garden center staff may have additional suggestions based on a more detailed understanding of the planting site you have in mind. If you have your heart set on a certain clematis you could always experiment and see how it does.
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