I have some clematis in containers. I try to get the largest container I can. You don't want it too big though because if you live in a cold zone you want to be able to pick it up and move it to something like an unheated garage when winter sets in. If you keep it in a room that's a litle warm the clematis will grow throughout the winter and you don't want that to happen. I did that before and it wasn't very healthy for the clematis. :) If you think things will get too cold you can insulate the container by wrapping it in bubble wrap or something similar. If you leave some room/a lip in the pot (which you should have done for watering purposes in the summer) you can also fill that empty space to the rim with the mulch of your preference. That will also help insulate your clematis. For the container mix I like to use bark chips as the main ingredient. I do this because in the past I have added too much peat type content and when you do that the soil becomes compacted rather quickly. The heavy use of bark chips makes it airy, light and the container will drain better. I also like to add some vermiculite and perlite. The other ingredient I add to the mix is a peat based mix by either Fafard or Scotts Metro Mix. Some sand can be added as well and contrary to some beliefs, it does not turn to cement! :) For a support I use both obelisks and trellis. I push them down into the pot until they are stable. During the warm months I usually water every other day and fertilize lighty a few times per month. For fertilizer I use 3 kinds. A dry All Purpose Fertilizer (6-10-10) sprinkled on top, Schultz liquid Tomato Food (9-10-15) plus micronutrients and Schultz liquid Bloom Plus (5-30-5). After winter is over, the danger of frost has passed and your clematis wakes up from it's winter nap you can spruce it up by trimming any dead stems/leaves and bring it outside. I'll leave the pruning details to the other FAQ. :) Most people will grow the smaller group 2's and some small groups 3's in containers, but I don't discourage people to experiment with any cleamtis they like. Hope this helps.