I have a potted arborvitae approx 4' tall that is starting to topple over at the top. Can I prune it?
Pruning Potted Arborvitae
Certified GKH Gardening Expert
Arborvitae don't take well to pruning. You can do it but it may result in bare spots or mis-shaping in the plant. Your better course of action is to repot the plant into a bigger pot and this would stop the falling over.
If repotting is not an option, you can prune. Just proceed slowly and realize that if you cut growth off near the top, you will permanently restrict the height of the plant. You should only prune to reshape the plant and any deep pruning (where you cut off entire branches) will not likely grow back.