Posted: 12/06/2012 at 17:49
When you first mentioned drainpipes I was going to say "anything BUT wisteria". I've just had to remove a beautiful wisteria floribunda from under MY kitchen window because it kept legging it up the drainpipe right to roof level and awa,y and was forever coming in the windows! 30ft + didn't sound that much on the label all those years ago, but it really is. Wisteria sinensis is even bigger, maxing out at 100ft. To get flowers you need to prune wisteria quite carefully twice a year, so it isn't low maintenance. If you don't prune it well and keep tying it in for a few years until the woody framework forms you end up with a huge green hummock without much to recommend it. That said, if you're up for the effort, they're spectacular.
What about trachelospermum jasminoides? Looks a lot like jasmine, smells lush, is evergreen, frost hardy, and is a fair bit bigger ultimately than jasmine or sollya at about 25 feet max. Pretty seed pods after the summer flowers extend the season of interest. Wonder if you could pair it up with an early clematis for the best of both worlds...