I sow my seeds into heated germination flats and transplant, when ready, into cell packs. This was how I was taught to do it in college, how I did it when working for a commercial business, how I taught hundreds of students to do it, and how I did it myself when I was growing thousands of bedding and vegetable plants. I still do it this way, now that I'm only growing a few hundred plants. It's efficient, convenient, and beneficial for the plants. I can sow 100-200 seeds into one plastic flat. I heat mine with heating cables buried into the germination mix. My successful transplant rate from the crowded germination flat is exceedingly high, probably 98%. Young seedlings don't falter for one millisecond due to this second step...rather, they burst into rapid development. I use a much coarser potting mix for the cell packs, to be sure. The cells I use are either 36 or 48 to the sheet, plenty big enough for a hefty, sturdy plant ready for the 'real world'. They can stay in a cell that size for several weeks, waiting for conditions to be right. I feel no need for a larger finished plant. The smaller ones catch up to the larger in no time, anyway. Why do I propagate this way? The germination medium is, by necessity, fairly fine textured (ProMix) and I absolutely do NOT want to grow any plants in that stuff for more than a few days after germination. The few flats that I heat take up very little space and once transplanted, I'll only use 9 or 10 liners filled with the cells. That makes it easy enough for me to take them outside during the day and bring them back in at night, if the temperatures are too low. Seedlings are much tougher than people realize. When grown properly, their stems are sturdy and springy. Though I sow them VERY close together in the flat, they prise apart very readily and without detectible damage. The filled cell packs will be pre-drilled with little holes so that the seedlings plop right in. I do one flat at a time, watering them in thoroughly with my misting nozzle when done. One thing to remember is that root systems will regenerate and regrow rapidly. This is true for all kinds of plants. As a matter of fact, root pruning is how we encourage a flush of new root growth in woody plants and houseplants. The fibrous roots of young bedding plants are not likely to cause the seedlings any problems at all during a proper transplant process. Here is a link that might be useful: flats and cell packs

Evey, owner of a website that specializes in small clems for containers, sent beginner-me a very informative reply to my questions. The website says they are sold out of everything right now but there's lots of background info on zone, sun/shade, & height. Then the super experts in this forum can help you make a final choice! I bought a nice Princess Diana from them to plant in the ground, but Evey grows it in a container: http://www.simplyclems.com

Do they have any flowers or buds on them now? If so, I would enjoy the flowers before cutting back. Otherwise, you can do so now. As with ANY clematis, plant deeply (3-4" deeper than container soil level) in a well amended large planting hole in an area of excellent drainage. You can cut back hard at time of planting (see above re: flowers) or wait until late winter and prune back to 2-3 sets of buds above the soil. Since this is a type 3 clematis, you will want to follow this hard prune practice each season. The deep planting and hard pruning will encourage a healthy root system and multiple stem growth.

Are you moving them to pots permanently? I just ask since I wonder what will you do in the fall when it's getting cold again? That could help decide if they would be moved to pots or not. However, besides thinking of that future scenrio, you can move them to pots now. But just be aware that digging at it will usually cause accidental breakage of some stems, so just know you may not get it as intact as you hope. As for the root ball, you can remove excess dirt, even long root hairs but you don't need to wash out all of the soil.