I planted four different Clematis's last year. Two of them flowered. This year there growing like crazy but still no flowers. I have them climbing on about a three foot fence and there hanging over the fence. If I trim off whats hanging over will this promote buds?
No, don't trim them. Clematis can take a couple years to really get established. Wait it out and they will bloom eventually. The roots need to really get going before they will bloom, but once they do, look out.