The American Pillar Arborvitae (the original sport* shown at the left), grew to 21 feet tall and only 4 feet wide in 7 years from an 18" plant in a field of 500 ordinary Thuja Arborvitae...
The American Pillars were spaced at 24" intervals and were approximately 4 feet in height. 2 1/2 years later The American Pillars stand at approximately 9-10' tall and just under 3 feet wide in picture at below...
This picture at right is the same stand of trees, standing at 3 feet in diameter and 18-20 feet tall, just 5 years after planting the original 4 foot tall trees.