Greg, In my landscaping business, have pruned ANY kind of shrub ANY time of year for a kazillion different reasons. The key to pruning is WHERE you prune it. Be sure to cut right above a leaf node because the wood will die back to a leaf node on ANY shrub. Although there are some shrubs that you can shear straight across, a pussy
willow is not one of them. Knowing a shrub's natural
growing shape helps one tremendously in knowing the proper shape to prune it. Too often, one will prune a shrub to be wider at the top, which puts the lower branches in shade of the upper branches and they eventually die off, leaving only foilage at the top. Drive around your neighborhood and you will see many junipers like this, poor things! For your Pussy
willow, prune it a bit oval, a bit skinner at the top. Since pruning at a leaf node will cause the stem to grow two more branches, this is a great way to grow a fuller shrub as well. Good luck! Becki