WHen is the best time to prune a Weeping Birch tree?

Answer 1

Fall, right after the tree goes dormant, is really the best time to prune any major limbs from a birch tree. There is less chance of shock after the tree goes dormant.
The next best time of year to prune is early spring, after the new growth begins to appear, but you want to focus on only pruning back new growth that may become problematic, such as root suckers, or new shoots in or near the bottom fourth of the trunk. This is also the best time to cut back dead or diseased limbs.
If you mean prune now, no, not really. Only cut off right now dead limbs, or ones that have been clearly attacked by a pest, and maybe remove a few of the sprouts off the trunk here or there, but keep it very light, as the rising heat may send the tree into shock. If you do prune that much, make sure you deep water the tree and add a fertilizer to help the tree recover from any shock, and encourage healthy growth.
Good Luck

Answer 2

When To Trim Birch Trees

Answer 3

right after it flowers or in the spring before new growth appears!