I've planted them around 4-5 metres apart. The montana should flower up till June and the madam julia from June to September, fingers crossed it goes well but doesn't get out of hand. I have left a couple of metres gap with no trellis so they should stay separate I hope. #still-learning
Our garden is still quite new really. We moved in 4 years ago to overgrown dead grass everywhere. There was just montbretia, flax and a small cabbage tree in the front garden. We are a million miles from that now. The two clematis I bought are in addition to my 1st an india star that I bought last year.