Clematis seeds

[Palustris]

Not sure if I should ask this here or in Basics, but it is Non edible plant info. Has anyone tried sowing Clematis seeds in the 'green'? I have grown herbaceous clematis from fresh brown ie ripe seed with some success, but just for an experiment this year I was going to try C. viticella types. The seed is still green and not likely to ripen if the weather gets really cold, like it is supposed to. So are Cleamtis like some Ranunculus species and grow from unripe seed?