Guernsey Donkey2 Posts: 6,713
Approx. 2 - 3 years ago I grew a plug clematis Montana Rubens and at the appropriate time we bought a trellis and what we thought was a decorative pot large enough for the clematis to grow and flourish in against a south facing wall. Well it did grow and flourish and produced half a dozen flowers in it's first full year and this year we have a couple of dozen flowers at least. Some of you suggested that the pot we had bought was too small, however regardless of this sound advice we planted and of course you were right! Instead of having flowers the size of saucers which is what I had been told to expect we have flowers the size of 10p pieces! Lesson to be learned is this - if you ask for advice - take it! You will see the flowering plant and the new pot in the pictures. We are planning on cutting the clem down after flowering and repotting - say about Sept/Oct.
Nice pot, but I think it'll still struggle to fulfill it's real potential. Is there no chance you can get it in the ground GD?
I live in west central Scotland - not where that photo is...
I'd say the pot is just limiting the amount of flowers you're getting; ours is the same age in the ground and when it flowers it's smothered in them.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
My experience of Montana is that I love it for early flowering, but pay it little attention after that apart from a good cut back. I would never grow it in a pot for very long.