Topping and pruning
Does it harm arbavida to top it. I have been told over time it would kill the tree. Is this true?
Yakima County Washington
Actually, arborvitae is one of those trees that respond well to shearing into shape for a formal landscape. https://extension.colostate.edu/topic-areas/yard-garden/hedges-7-208/
Be careful, though, not to cut into the area where no leaves are growing. Arborvitae does not have latent buds on internal bare branches. This area is called the “dead zone” – these shrubs must not be pruned back beyond live foliage--it will stay dead and never show any new green growth. You would not want to shear back an established tree, as the inside of it is completely "dead zone." It's best to start with a young tree and "train" it. Sheared trees will require regular maintenance.
You can shear it before the spring growth starts to hide the pruning cuts, or wait until late spring when there is lush new growth. Be sure to shear the bottom slightly wider so that light can reach the lower part of the hedge.