Recommendations for a climber through a hedge?
The key requirement here is the climber needs to be vigorous enough to make a good showing between the hedge's cutting times. So, for example, while a Montana might be good, I'm guessing other clematises wouldn't be able to make much impact. Bindweed already does very well on the north-facing hedge I have in mind, so maybe the purple version, Ipomoea purpurea, would do well? We typically have -5c in the winter, getting down to -10c every 5 years or so. I'm on alkali, free draining chalky soil in SE England.