Is this the one they call 'Flamingo Willow' lovely greeney/white foliage going to pink looking like a flamingo standing on one leg? I planted three of these small trees in a border a couple of years ago. By the autumn of year 2 they were quite straggly looking, so I took a pair of secateurs and gave them a gentle haircut, cutting back the long whippy branches and creating a gently 'rounded' shape. This Spring, just as the leaves were beginning to burst, I took out all the dead wood and any that looked like they might become brutes as the Summer wore on!

My little trees, they are only 4 foot high, now look soft and shapely standing in the border.

Good Luck