When in the past I have tried to propagate a difficult-to root variety, I was advised by an experienced nurseryman that if you soak the cuttings for a few hours in a solution of warm water and dissolved aspirin tablets that it would help. As I remember, I took about a half dozen tablets, dissolved in a quart of water and soaked the cut ends of the roses in it overnight. The variety I remember trying to root was a hybrid tea, "Matterhorn", fairly weak grower and thus less likely to root on its own. I had tried a number of times before with no luck but when I used the aspirin method I was able to get about a 50% success rate. I have since read that aspirin has the same chemical compound as the common willow and I remember many years ago my grandmother soaking willow stems in water and then pouring the results on her garden. She always had a good looking garden, so maybe there is something to it after all.

Good luck and if you have a cutting or two to spare, let me know. Sounds like something Id like to have also.