Though they will perform OK in semi-shade, the more sun the more bloom. Salix will take wet conditions, and though they are adaptable to normal-to-slightly dry soil as well, bone dry will also make the plant unhappy. Any chance thing sare too shady or too dry?
I do a lot of judicious pruning of trees that are overhead of my shrubs borders (or have someone come do it if the trees are big) — just taking out a few branches can really help change the light pattern in an area, and you still have the tree. I am not sure of you mean think the pussy willow itself or overhead branches (as I am suggesting)?