Here's the best source of information that I know of: Brian Collingwoods' site. Suzymac who often post's here has a lot of experience growing clematis from seed. By searching for 'clematis from seed' in the search box at the bottom of the forum page you come up with a lot of information. Here is what I got when I did so: Search Results

I've done it, using Brian's site to lean on. It takes me a far longer time to achieve results than it does for him in England with a greenhouse.
You'll learn a lot about patience.

Another one who has done it using Brian's info from his website. Just realize that 1) as Marie said, you must be patient since some clematis seed can take up to a year or more to germinate and 2) growing seed from a hybrid clematis plant may give you a plant that looks similar to the plant the seed came from or may give rise to a new clematis plant that looks entirely different than the parent plant.

I am assuming you were given Polish Spirit seed to germinate which a viticella type clematis. On the page below from Brian's website (all the way towards the bottom), you will see a listing of germination times for various clematis seed. You can see there is a lot of variation of germination times even amongst the viticella types Brian has listed so patience is the key. I too have found that generally it takes far longer times to achieve germination than the results Brian lists--possibly due to the lack of a greenhouse.

Here is a link that might be useful: Germination Data

Adam, one other thing I forgot to mention. Winter sowing may work well for some clematis seed, however the point to remember that was mentioned previously is that some clematis can take quite a while to germinate. If you winter sow some clematis seed and they haven't germinated by early spring, you need to make sure you keep the pot, seal it up in a plastic bag to maintain the soil moisture level, and place the pot in an area that is constantly shaded or the sun could cook your seeds and any plants that do germinate. Check the bag weekly or so for germinations. If by the next fall, nothing has germinated, put the bag containing your pot of planted seeds into a cool area inside an unheated garage or something similar and keep a watch on the pot over the winter. Some clematis seedlings may germinate sometime along the way.

Thank you all for that great info and the links. I definitely will try the winter sowing and adjust my expectations. [g] thanks nkvilledudes for the additional instructions for what to do if they aren't germinated by spring. Boy you need a lot of patience for this one!

:-)

adam