How large are the pots? I would plant annual vines if you want fast growth and flowers. Morning glories, moonflowers, black eyed susan vine, and mandevilla are a few that come to my mind and I read that all can be grown in containers. Combining morning glories with moonflowers is a good idea, having flowers both night and day. You're a zone colder than me and I usually don't get moonflower blooms until mid August at the least. Starting them early indoors (The method I used was I wrapped the seeds in a moist paper towel placed in a plastic sandwich baggie and placed in a warm, sunny window) will be a good advantage. This is my first year sprouting moonflowers indoors and I had great sucess with them.

I've never grown mandevilla or black eyed susan vines so I can't tell you much on those. I've seen pictures of them and both have nice flowers. Sorry to ramble, but I'm one of those talkative types. There are nice people on here willing to share their advice as well.

Brad AKA Moonwolf

Are morning glories easy to germinate?