I have been growing clematis on a trellis in full sun for a few years now. My trellis is only 4ft high and I don’t want to increase the height as it will block out the view of the rest of the garden. In past years I have just let them grow and then either weave them in or let them “fall over” once they are taller than the trellis. By the end of June, they are quite a mess! This year I have tried to pinch back weak new stems to maintain a 4ft height and hopefully increase leafage and flowers lower down. However I have read that by pinching of this new growth may delay the flowering or even grow lots of leaves but few flowers.
What do you think?
You definitely need to prune your clematis.
Here is an informative Toronto Master Gardeners post that describes how to prune clematis depending on their blooming time:
For more information:
Good luck.