How To Prune Arborvitae ‘Green Giant’

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

79 Comments

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.

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

    1. Mike K Says:

      I have what was 2 great trees that took a beating this winter
      Can the trees be that are over 20′ be trimmed down to about 8′ and live ?

    2. Roger Says:

      Jessica, that should be fine. Often we can’t reach the tops to be so precise with our cuts either. The plants will continue to push new growth and maintain a leader.

    3. Paul Tomczak Says:

      I ordered Emerald Greens from a mail order nursery years ago and was very happy with the plants, although they were subject to scale on occasion. I’ve been looking around at local nurseries for additional plants, but the Emerald Greens don’t quite match what I received by mail. The local plants all have branches that are oriented to the vertical, whereas my Emerald Greens have branches that are more horizontal, giving a sculpted look that I prefer. Are there different varieties of Emerald Green? Thanks!

    4. Roger Says:

      Tammy,
      Arborvitae prefer a neutral pH soil. Plant-tone would be great.

    5. Roger Says:

      Brian,
      You could prune the top leader back to a certain point. It’s hard to give a definitive amount to cut back because situations vary. But think in terms of always maintaining a pyramidal form. So prune the top (crown) as a whole and see how the aggressive shaping at the top (maintain the leader and pyramidal form) allow you to cut back the leader’s height. I hope that makes sense. I really have to start doing simple videos to demonstrate things like this.

    6. Roger Says:

      Richard,
      Tough to tell without seeing it. You’ll have to wait and see – so hold-off on any corrective pruning till the season progresses and you clearly see what’s living and what’s not.

      The plant can push new buds and growth in some circumstances. However, any stems or branches that had their bark stripped off will likely die back. This outer layer (cambium) transports nutrients, and when it’s removed that causes that section of the plant to die.

      It’s those portions of the plant with bark remaining where it’s possible to re-bud.

    7. Roger Says:

      Mary,
      Interesting. In our area ‘Green Giant’ is called deer resistant. This is just another example that “deer resistant” plant lists should be taken with a grain of salt. And just the other day I had a long conversation with a person who operates a deer control business. And he was telling me of many instances where deer were behaving differently than industry reports & lists were stating. In short, it’s not an exact science by any means.

      To answer your question, yes, you can elevate the trees to remove the damaged lower branches. The tree will be fine. And actually, it can look quite nice.

    8. Roger Says:

      Mike,
      The trees must be in really bad shape to have to cut them back to 8′.

      Without seeing the trees it’s hard to even comment, but this is my thought: If you’re cutting them back from 20 to 8′, I have to believe the tree is not only compromised health wise, but disfigured too. Perhaps you should think about replacing them. At least the new plants (at 8′) will be attractive, healthy and ready to grow.

    9. Roger Says:

      Paul,
      I feel your pain. I too have experienced variations in plants when they are labeled the same. I can’t say for sure why this happens, but it’s not uncommon.

      Trust your judgement and wait till you find the leaf type and habit of growth that resembles the euonymus you have (and like). It’s great that you’re that observant.

    10. Cari Says:

      The other day I thought I could diy prune on my green giants. Well my husband said I have ruined the tree. The 2 trees are in my front yard. Right when you walk in. I didn’t trimmed them since I lived here for the past 2 years I lived here and IM pretty sure no one did before I moved in. The growth was so crazy I couldn’t walk into my house without bumping into them. So I borrowed a friends hedge trimmer and got to town. Parts I had to cut off to walk into my house are not “green” its the stick part. My husband says I ruined the tree. But I have researched that the tree is a rapid grower. Will the tree regrow the green? Did I damage the tree? I cut so much of it off.

    11. Tom Says:

      Hi,

      Just planted mine this past April of 2014. They are 8 feet in height. What time of year should I prune them? I live on Long Island NY.
      Thank you

    12. Roger Says:

      Cari,
      Hard to say without seeing it if the plant will recover in the areas cut back severely.

      It sounds to me as though they’re simply in the wrong spots. Any chance they could be transplanted?

    13. Roger Says:

      Tom,
      We do most of our pruning in late summer.

    14. Dalya Hakimi Says:

      We live in New Rochelle New York. zone 6. We need a fast growing deer resistant hedge and the landscaper is recommending Arborvitae Green Giant. The problem is I never want it to get higher than 10 feet or so. Can we keep it pruned to that level?

    15. Roger Says:

      Dalya,
      Arb. ‘Green Giant’ would be impossible to keep within 10′. You might consider Skip Laurel (Prunus laurocerasus ‘Schipkaensis’).

    16. Melissa Says:

      Hi Roger — I am afraid we messed up!

      We planted some 8 foot green giants last fall and they did amazingly well — grew about 1 foot in 6 months, but super skinny growth on top and quite thinned out. We tried to follow the pruning instructions and cut the skinny part down about 10 inches to help encourage full growth, but now about 3 weeks later, some of the branches that previously were below the top point after the cutting (so previously helped shape a pyramid) have now grown higher then the top point.

      I am concerned this might create a double leader and that the original “top” leader won’t grow. Can we trim the other branches back a bit (both vertically and horizontally) to get the pyramid shape at the top back? Is there something else we should do? Thank you again for all of your advice and help!

      –Melissa

    17. Arlene Says:

      Hello. We just set out 9 Thuja Green Giants along a 45-foot fence row. They are planted about 6 feet from the fence. We want the trees to reach a final growth of about 18′ x 8′. Can this be achieved with pruning, and if so, when do we start pruning them and how? They are very tiny now.

    18. Brent. Says:

      Hello out there.
      Should I prune my Green Giant so that it has one main trunk?
      Currently it has one large trunk and two smaller ones with all three starting at ground level.
      Thank you!

    19. Susan Says:

      Last fall I wanted to trim my pyramidal’s so they would be straight across. My friends (they still are) topped the center instead and they look awful. Will the outside grow up (eventually) to cover the ugly stick now showing? I’m so sad that they wrecked the nice shape.

    20. Robert Says:

      Hello Roger, great information. I have seven Giant Arborvitae that were planted five years ago. I fertilize they and mulched for the first couple of years. They have been growing steadily so I just left them alone. The trees are over fourty feet high and about twenty feet wide. They look good but My question is pruning it. Do I just let them grow. They are not restricted. I enjoy the wildlife that uses it for shelter and they provide privacy.

    21. Chris Says:

      I’m thinking of using some green giants for a second level deck screen. Is it possible to keep them between 16-20 ft?

    22. Bryan Esposito Says:

      Roger, I have a row of 10′ GG planted 8 ft apart. 3 of them have been damaged (broken branches) on one side by a miniature horse rubbing up against them. I have since fenced them off. I’d like to dig up and rotate the trees 180 degrees so that the bare spots where branches were broken are facing away from my house. What do you think about this idea? Would I risk losing the trees from stress? I am replanting them in the same spot, just turned. Thanks!

    23. Roger Says:

      Bryan,
      Yes, you can dig and rotate them. But make sure you’re digging the plant correctly. Also, if possible I’d wait until early fall (Sept.). It will be less stressful on the plants, and yet still give them time to root before winter.

    24. Roger Says:

      Melissa,
      Perhaps that first cut of 10″ was a bit much for an 8′ high plant, but I still think you’ll be OK.

      I would do some additional pruning/shaping, as you’re thinking, on the growth at the top and moving downward. Envision the pyramidal form to the top and draw an imaginary line to that effect. Prune/trim to follow that imaginary line. Don’t feel you have to get it cut way back to make the remaining central leader at the very top – that could be too aggressive on the nearby growth. Think of it as a “beginning campaign” to eventually allow the central leader to dominate…as it should. This could take another year or two for it to happen.

    25. Roger Says:

      Arlene,
      I think your plan to have the GG’s grow to 18′ X 8′ is realistic, however, not without controlling them with pruning.

      Start now by just tipping the end growth with shears to encourage fullness. I would take note of the size each season just so you have a record of how fast (and big) they’re growing. This will be helpful in understanding their rate of growth and guiding you as to how much (and how aggressively) you should be pruning them.

      They’ll come a point where you’ll need to prune decisively to keep them in check.

    26. Roger Says:

      Brent,
      Depending on how old and tall the plant is, removing the 2 smaller leads may be too drastic a step.

      Alternatively you could allow the 3 stems to remain. With multi-stem arborvitae we use a product called Arbor Tie to make a supportive loop about 1/4 from the top of the plant. You can discreetly weave the Arbor Tie inside the plant branching around the 3 stems. This will prevent the 3 stems from splaying apart, particularly when it snows heavy. Every 3-5 years you should check on the Arbor Tie because it may have to be moved or adjusted as the plant grows. Do not use rope, twine or wire for this – it will harm the tree.

    27. Roger Says:

      Robert,
      Those ‘Green Giants’ are living up to their name!

      If you have the room to let them grow, they’ll be perfectly fine on their own. The plant typically has one central trunk & leader and grows with a reasonably strong framework.

    28. Roger Says:

      Chris,
      I’d hesitate to say that you could keep them at 16-20 ft. long-term. Even with annual pruning they will eventually want to get larger.

    29. Roger Says:

      Susan,
      I’d have to see them to give a better comment, but it sounds like your friends cut the center stalks fairly low.

      The tree(s) should instinctively grow and branch-out where that cut was made. If you want them to get taller you should notice one or two branches aspiring to become dominant and grow upward. You could allow this to happen and slowly get back to a single, dominant leader.

      If the height is close to where you want it, you’ll end up continuing to trim the newer growth that occurs in that area to control the height. Eventually this should all fill in at the top and hide the cut.

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