My Nellie Moser clematis, the kind with the pink and white stripes, did not bloom well this year. The flowers were smaller, color washed out, and didn't last long at all. It did well last year but still isn't a very big plant for as long as I have had it. I have it growing behind a fairly large azalea, to shade the roots, but I am wondering if the azalea is too big, and blocking too much sun from the plant. Could this be the problem or are there other reasons for a clematis to not do well?