How To Prune Arborvitae ‘Green Giant’

How-To's, Landscape Care · Written by Roger


shear.arb.ggThe Green Giant’s Growth Habit

Perhaps I’ve said it before, but it’s extremely helpful when you know what a plant’s growth habit is before you prune.  Growth habit is basically the shape a plant naturally wants to grow into and how the branching structure supports that shape.  For example: Arborvitae ‘Green Giant’ is pyramidal in form and proportionately much taller than wide.  As a matter of fact, this plant will easily get to 30′ tall and 15′ wide in thirty years.  Rapid grower…I think so.  Its branching structure is horizontal with some ascending branches as well.

Other characteristics about the plant can be helpful too when deciding your pruning strategy.  For instance, Arborvitae ‘Green Giant’ prefers more light (full sun is ideal).   The less light it gets the thinner and more open its branching and foliage will be.  Prune less aggressively if you know the plant is adapting to less than ideal conditions.

Before Pruning

The Pruning Strategy

Let’s assume the ‘Green Giant’ you’re going to prune has been positioned to have enough room to grow and stay somewhat within its “natural boundaries”.  If the space is too limited and there’s no future for the plant in that spot, think about transplanting it.

To give ‘Green Giant’ a strong trunk and branching structure, it’s important to prune them in their early years.  In the first picture above, these Arbs were undoubtedly pruned early on in their lives.  Notice how full they are from the ground to about 4/5ths of their height.  However, the last growth at the top is thin and “stretched-out”.  This is very typical of rapid-growth plants.

It is this top growth (upper 1/5th) that needs pruning.  You should also scout the lower portion of the plant for any branch ends that may have grown more aggressively than others.  There should not be many.

After Pruning

I apologize for the picture quality of these “before” and “after” shots, but even the silhouette conveys the degree of pruning I did.

I used a traditional trimming shear along with an orchard ladder.  By today’s standards you might call that “old school”.  I still think a good quality hand shear gives the best cut and, of course, with total control.  I did, however, think how convenient and productive a telescopic gas powered shear would have been.  Just take care as those power shears can cut aggressively.

The main goal and concept here is to trim the ends of the longer, fast growing branches to shape the plant and encourage fuller growth.

This is what plant nurseries do while they’re growing the plants for market.  You want to continue this trimming routine for as long as it is practical.  The idea is to develop a full, nicely shaped plant so that it can continue to grow on its own with this strong foundation you’ve help create.

Be Sociable, Share!
    , , , ,

    103 Responses to “How To Prune Arborvitae ‘Green Giant’”

    1. Jim v Says:

      I have a row of Arbs which were present when I bought my house 14 years ago. They are now a nuisance to my gutters. I don’t want to give up the “natural” fence between my neighbor and I, as their lawn care leaves much to be desired. would it be okay to trim them from about 15-20 down to 10ft? transplanting isn’t an option, since there is a gas line and sump pump line within 3ft of the base of the trunks for about 75% of the length of the row.

      Also, I have another row which is encroaching on my driveway on the other side of my property. I am contemplating removal of those trees as they are 20 ft tall as well and trimming them back at this point will leave them quite bare on the southern side. how deep does the root structure go if I were to decide to do this, or how aggressive can I be in trimming them back from the driveway? I would likely need to cut out about half of the radius on that side.

    2. Roger Says:

      As you’re suspecting, cutting the Arbs down from 15-20′ to 10′ is pretty extreme. I’d have to see them to give real guidance on how much to cut.

      The plants will survive the cut, but the uncertainty is how they’ll respond and look at the top where they’re cut. The Arbs naturally want to have a central leader that grows in height. You’re proposing cutting that back a lot and then essentially maintaining it there — for as long as you can anyway.

      I suspect the side branches just below your cut will push out growth (during the next growing season) and you can begin to “round-off” that top growth to keep the plant from getting taller.

      Please keep in mind this is just my opinion, and I have no way of being sure how your plants will react to severe cuts like this.

    3. Roger Says:

      I realized I did not comment on the second question you had regarding the Arbs along your driveway.

      Cutting half the radius of the plant’s branching would look terrible and likely not recover — at least to an acceptable appearance.

      The roots on an Arb that tall are approximately 24-30″ deep. And just like you’re aware of underground utilities with the others, I’m sure you’re considering the same with these. Also, I’m sure you’re taking into consideration the impact on the driveway. Loosening the base material (of the driveway) near the edges should be avoided if possible. You might have to do some preliminary “hand digging and root cutting” before you pull the stumps.

    Leave a Reply