No worries, you can transplant those potted clematis in spring or fall or even during the summer if you must. You can cut back the clematis to one foot tall right after they flower in the spring or if they are summer bloomers sometime in early spring when you see signs of new growth. The trick is to not damage the fragile stems as you remove them from the containers. Soak the soil well and then try to dig them out and do not fret if the vines separate so you have many separate plants. The important part is that the stems are not broken as this can lead to an entry for clematis wilt disease. I would prune the vines back before you move them. I just removed my own clematis from a container this March and the newly transplanted vines became not one plant but four plants. No flowers this year as the plant must grow roots but you can expect blooms again in two to three years. Dig a wide, deep hole and loosen the surrounding soil when you plant clematis into the ground. One foot deep and three feet wide is about right. Mulch the top of the soil to keep it cool. Clematis like their roots in the shade and tops in the sun. I think you will have a lot of new clematis - I grow mine next to shrubs and trees that can act as natural support for the vines. Keep growing, Marianne Binetti