Weeping river birch trees, known botanically as Betula pendula Youngii, do not require frequent pruning for healthy growth and performance. The can however benefit from occasional trimming to keep the canopy looking groomed and tidy. If you prefer a manicured or topiary look to the bottom of your weeping birch canopy, a level can be used to help execute a crisp trim line. Light trimming can be done any time of the year.
Trim away any dead, damaged or diseased looking branches back to a point of healthy wood or all the way back to the main branch or trunk. Pull the cutting free from the canopy and discard or compost it.
Hold the level against the tips of the weeping branches at the finished height you desire. Adjust the level so that it is plumb at this height. With your pruning shears in your other hand make several guide line cuts along the line of the level.
Set the level aside and pruning shears aside and pick up your long blade scissors. Hold the cutting blades parallel with the bottom of the canopy at the guide cuts made with your pruning shears. Cut the branches along this line working around the tree in concentric circles.
Pick up the level periodically and check your work to make sure the canopy line is level in all spots and correct any imperfections in the level line with your scissor shears or pruning shears.