The arborvitae requires trimming once a year during fall or winter. Visualize the shape you want to give the tree in order to identify the areas that need to be trimmed, and only cut the vertical growth outside the intended shape. Avoid cutting into dead zones, areas that feel bare and areas that don't produce new growth. Avoid cutting horizontal growth to allow the center of the tree to receive sunlight and to reduce the appearance of dead zones.
Keep a maximum of three competing leader branches, and remove the remaining leader branches as close to the ground as possible. Remove very thick competing leaders by cutting gradually in three parts, starting one-third of the way down from the tip of the branch. Make the second cut at the half-way point of what's left of the branch. Then cut as close to the ground as possible.
Cut off damaged and deceased branches 3 to 4 inches bellow the damaged wood to encourage new growth.
Trimming the arborvitae is important to control the size of the tree, maintain its shape and reduce the chances of pest infestation. Protective gloves are necessary to prevent injuries. Always sanitize your pruning shears with rubbing alcohol before and after trimming to avoid the spread of disease.