If you want them to grow together as soon as possible don't cut them back. To encourage maximum density grow them well, so they are full and healthy. When arborvitae are thin and scraggly it is due to poor site conditions.

A hedge row of ÂGreen Giant was planted on the grounds of the U.S. National Arboretum in 1998. At the time of installation, the trees were 3  3 ½ feet tall on 6 ½ foot centers. Ten years later, the trees stand 18  20 feet tall and 8 feet wide

Here is a link that might be useful: A Jolly 'Green Giant' Spotted at the National Arboretum

To get fill above the basal skirt on a conical conifer you have to wait for the hedge to get to get tall enough for the branches to have grown together at a higher level than in the early years.

If you are talking about topping and shearing it into a rectilinear formal hedge, then you are setting yourself up for quite a chore.

Every spring.

Agreed. If arbs....any arbs...are happy in their surroundings and in sufficient light. they develop very dense structure on their own.

While arbs are one of the plant types suitable for a shearing treatment, this is a lot of work and if you ever decide it's just too much and quit the procedure, you will have very ungainly trees-extremely dense up to the point where you quit the shearing, and quite a bit rangier and thinner beyond. Plus, new, rangier growth will always be erupting from the lower sheared part, and this will not look pleasing.

So, if at all possible, go for their normal natural growth form. They screen very well just as is.

+oM

"Ten years later, the trees stand 18 Â 20 feet tall and 8 feet wide", and that will continue at 1-2 ft/year in height. Finally the width will be 20 ft.
My former neighbor planted them just over the property line, and I am pruning them back , now on ladders, so my c.nootkatensis 'Pendula' can live. What a pest!
Bernd

This is what can be achieved in 10-12 years if left alone.

Dave
{{gwi:637326}}



{{gwi:637331}}

Beautiful hedge. The owners knew the future size of the trees and planted them accordingly, with all parts of the trees in the future only on their own property.

Actually, if that hedge gets as big as the National Arboretum says the tree gets...