I have a northwest facing wall, where I currently have a Clematis Jackmani growing against a trellis. I have had it there for around 10 years now, and I only ever got a few blooms per year from him. I would like to replace him with a variety more suited to this aspect.

As I mentioned, it is a northwestern exposure. However, it does not get any direct sun, because there is a row of very large, mature, deciduous trees, about 60 feet away, that block any direct sun. There are no trees, shrubs, or overhanging branches anywhere close to this location, so although always in shade, it is "bright". The wall itself is a very pale yellow, which helps to reflect what light there is. I am in zone 6a, NJ. Can anyone suggest a Clematis that would work for me?