Cobaea scandens 'Purple' will clamber up and over your garden wall. It is a fantastic, exotic looking plant with buds in green-white, deepening to purple as they age. I've picked a bunch of these in December on a sheltered wall in Sussex.

There is a seemingly unsolvable conundrum for the many gardeners among us who would like vertical interest and colour in summer without having to wait a year or two for shrubs or perennial climbers to develop sufficiently to flower well.