Hi, I have about 15 Flame Willow and about 15 Golden Willow that were planted three years ago as part of my Wind Rows. I let them do their thing for the first three years and now I would like to start transforming them into trees from their current form as shrubs via pruning. The soil is slightly ph, the gound floods for two or three days every few years. The plants are about 5 feet high with a good leader but dozens of horizontal branches forming a pyramidal shrub. I also have Bay Laurel that need to be pruned into trees from shrub. When is the best time to prune for willow specifically to assist in the morph from shrub to tree, how mush at a time 10% annual, 30% ? ' Thanks.