Answer: I think your clematis are just going through a little adjustment period and once they become accustomed to their new homes they should grow and flower nicely for you. In general, they like their "tops in the sun and their roots in the shade", so the roots may be stressing out a bit in a terra cotta pot if it gets direct sunshine. This can explain why the flowers are not as long lived as you expect them to be. If there is a way to shade the pots from hot sunshine (grouping additional pots in front or placing a large rock in front might help keep the roots cool. Good luck with your clematis!
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