Clematis: Ordered these and what size pot should I use, 3 by Gourd

Gourd wrote:
I just got back, these are photos I just took. One shows where I'm wetting the area full of sunflowers that ill pull out. I took one facing my studio to show the seven rised beds and the other two show the other side of the wall where the turtle pens are. It is so bright her and I can't tell how the photos look on the iPad.

The wall is at different heights. You can kind of see the 15gallon pots, they look small, but I planned to put trellisis in each one so that the Clem's climb over to the other side.