We have 26 arborvitae elegantissima planted last year. They are about 4 ft tall and we want them to fill in between trees to create a border. Will cutting off the leader cause more lateral growth?? Don't want to damage them but want fuller fatter trees. Thank you.
It's not good to cut off the leader. What happens next is side branches start competing to become a leader, and it weakens the tree.
Here is the advice of tree expert and professor Dr. Ed Gilman.
"Arborvitae does not tolerate pruning well since all foliage is toward the outside of the crown, but it is well-suited for use as a barrier, background, or specimen planting in a large landscape where it is properly located so pruning is not needed. Its distinctive appearance does not fit easily into natural or informal landscapes. It is often planted in cemeteries and referred to as Cemetery Plant.
Arborvitae grows moderately fast in full sun or very light shade and tolerates drought well once established. Sandy or loam soil is best, clay soil is only suited on a slope where drainage is good. "
What Dr. Gilman is saying is that arborvitae are a shell species meaning that the green part is like an umbrella covering the plant. If you cut it off, no green will come in its place and you will have a bald spot on the tree. One recommendation from Penn State is that you plant another row in front of or behind the the arborvitae, bearing in mind that you don't want to shade any of the plants. The inner row can be a fast growing shrub that you plan to remove when your arborvitae fill in.