This is quite a rose specific question, rather than vines in general, so I think maybe the Rose Forum will be able to give you more precise information. My initial thought is that 3 ft high is too low for ZD and that it will need to be trained down as its natural tendency is to grow up. It might work but it will be quite maintenance heavy to keep it where you want it. I don't quite follow your last paragraph. ZD is widely available container grown here so I'm not sure that will be a problem.

Here is a link that might be useful: Rose Forum

Hi floral_uk, I debated about which forum I should put this in, but actually, I think you pretty much answered my most important question -- that it would probably be difficult to keep this vine growing downwards. I guess it's just not a cascading plant.

I'll keep looking for the right vine. I think I will put ZD in my porch planter to climb a column though. :)

Thanks for the info!