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.

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    148 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.

    4. freddie c Says:

      Can I keep arbs at 15ft tall? I don’t have much space between my property and next door..any advice?

    5. Roger Says:

      Over time it will be difficult to contain ‘Green Giants’ to that size. And not just in terms of height, but width too.

      You can put up a good fight by diligent pruning and probably get a good number of years of use out of the plant.

      There are also what are called “Plant Growth Regualtors“. These products get administered to the plant and control their growth. I have no personal experience with them.

      And, of course, if practical and cost effective, you could transplant the plant and replace with something more appropriate for that spot.

    6. Dale Says:

      What trimming technique could be used so that the top 3rd of the tree could become more full so that there is less gap between the trees? Thanks!

    7. Roger Says:

      If you follow my advice in the article, i.e. to concentrate trimming in that top third of each plant, they’ll fill in nicely.

      Make sure you prune back the terminal leader (main vertical stem) because this dominant stem wants to get taller each year. You’ll have to allow the plant to attain some degree of its height, but in the meantime you’re controlling the rate of the top growth and encouraging a fuller plant.

    8. cynthia Says:

      planted 3-4ft Green Gaints about 5 years ago…didn’t know about pruning doube leaders out so now I hav a lot in my row of 20 trees that are touching now and about 6-7 high…it it ok to prune the double leaders now?

    9. Roger Says:

      Of course I’d feel more confident giving advice on whether or not to prune out double leaders if I could see the plants.

      But here are my thoughts. With your Arbs at 6-7′ tall you could still remove one of the double leaders and the plant would have plenty of future growth to adjust.

      Where on the plants (in terms of height) is the double leader occurring? Upper half? Below halfway point?

      Again, I’d like to see the plants to guide you more assuredly. Can you visualize how the plant(s) will look right after removing one of the leaders? Can you carefully pull the one leader you’d remove slightly away from the other to give yourself a view of how it might look?

      I’ll leave you with this point in the event you decide to leave the double leaders. When we install Arborvitae that characteristically have multiple stems (e.g. Arb. ‘Emerald Green’), we automatically put a supportive band of ArborTie inside the plant 1/4 of the way down from the top. This prevents the stems from splaying apart due to age, wind or ice & snow. You could do the same with your ‘Green Giants’. If you do this, you must remember to monitor those “ties” at least once/year. They will need to be moved and/or adjusted every now and then. This is very important!

    10. Marta Carney Says:

      I have a single arborvitae next to my front door that has grown to more than 15 feet. This winter the deer have climbed on my front porch to nibble away at it leaving the porch side looking very shabby to about 4 feet high. Otherwise, it is in good health. However, it is starting to dominate the house facade and I would like to trim it to give some space around it. Can I trim it to the trunk from the base to about four feet? And then top it off a bit? I admit it will probably look odd, but perhaps more interesting and shaped. I wouldn’t mind removing it, but it is growing in the corner where the porch and foundation meet, and it would be a challenge to get out of there. Also, is this the best time of year to trim it? Your advice is greatly appreciated.

    11. Roger Says:

      Pruning up from the bottom to raise the canopy 4′ is an option. We have done that in certain circumstances and with several different types of plants. It should look OK with Arborvitae ‘Green Giant’.

      And you can also start pruning the top to slow down the growth. But realize this plant wants to get considerably larger. I’m afraid eventually it will overpower the space. Your diligent pruning will extend the time before that happens.

      Now would be a good time to do this pruning.

    12. Lynda Says:

      I’m very new to gardening and I planted some Emerald Arborvitae in front of my house last year in Staten Island, NY. The center of one began to brown and look dried up by the end of the summer. Then the snow this winter damaged some of the branching. Can all of this be fixed? If so, what do I do? I have no clue how to garden and I really want to learn. Thank you so much!

    13. Roger Says:

      Firstly, did you read my article on ‘Emerald Green’ Arborvitae? It will give you a quick overview of the plant and its care.

      The browning in the interior of the plant is normal. It sheds older, interior foliage as the plant matures. Browning on the exterior can be a concern.

      They prefer a moist (not wet) well-drained soil.

      Also, in the article I referenced above I mention using Arbor Tie to help prevent the splaying apart of branches.

      Realize too that plants usually look their worst this time of year — after the winter. In May you’ll get a better representation of how they’re doing.

    14. John Says:

      Hi Roger, great read. My Arbs are probably 20 years old and have dead zones at the bottom 4′. There were overgrown burning bushes in front that created the problem. I’ve since trimmed the bushes. Will these trees fill back now that lights gets to these dead zones?

    15. Roger Says:

      It’s hard to say if the lower foliage will come back. I have seen new growth emerge in situations like this. It’s good you’ve removed the competing burning bush.

      The majority of the bare stems and branches are probably deadwood at this point. But I would allow a full year for the plant(s) to show where and if any new budding occurs. Then, next year you can clearly see where there’s life and safely prune out the deadwood (to the points where it’s live).

    16. Lynda Says:

      Thanks for the info. I read the articles you mentioned and they were helpful. I have one more question…do you recommend a specific fertilizer or mulch? Thanks again!

    17. Roger Says:

      I’m not a fan of regimented fertilizing. More often plants are being fed that don’t need it. A soil test should be the determining factor, but few people (and “professionals”) rarely do that.

      If you’d like to fertilize the Arbs, I’d use Espoma Plant-tone. It will supply general nutrients safely and condition the soil (to some degree) as well.

      Mulching would be helpful too. Just be careful how much mulch you apply.

    18. Brian Says:

      Hi Roger,

      I have green giants (planted about 5 years ago and are now about 15′ tall) that need pruning. Last year I cut about a foot off of the top leader branch. This year I would like to prune the rest of the tree. When and how is the best way. I reading that anywhere from late winter to early summer is ok, but I’d like to narrow it down a bit more. Also, how much of the branch should I take off?

    19. Roger Says:

      I’d avoid late summer into fall as you don’t want to stimulate any new growth at that time.

      You could prune now (spring) and the plant will have the season then to grow & respond to your pruning.

      If you like the softer look of the plant, you’ll want to “selectively prune,” i.e. prune back individual branches. This technique will help maintain that informal look while controlling the size of the plant.

      You could shear the plant (many people do), but that will give a bit more deliberate shape to the plant. If you do decide to shear, do that now (spring) and the new growth that follows will help soften the look a bit.

    20. Chris Says:

      I have several green giant trees planted on top of a retaining wall for privacy. They are 2 years old and about 12 feet tall. I cut the leader branch off a couple of them by approx. 12 inches to encourage the trees to grow wider versus taller. Since I cut the tip, will they get any taller or remain approx. 11ft forever?

    21. Roger Says:

      They’ll continue to grow towards their mature size. It’s in their DNA.

      Pruning does slow that down somewhat, and encourage fuller growth.

    22. Angela Says:

      I have several green giants. Most look ok but would like to prune (just scared to) and 2 look horrible from the winter. Hardly any leaves. Can pruning bring these back?

    23. June Says:

      Hi Roger- we live in Long Island, NY and have 15+ green giants that are approximately 15ft tall, that we would like to have pruned. The landscaper we hired suggested topping them off 4ft however we are afraid they will not grow back in the nice shape they are now. We suggested 2-3ft instead. Would they grow back even when the leader branch is cut? And is now a good time or should we wait until Nov/Dec? Our neighbors are complaining that the sides are overflowing into their space and so we are trying to maintain them now.

    24. Roger Says:

      Cutting 4′ off the top of a 15′ arb is a bit extreme. 2′ would be enough in my opinion. You could then prune the surrounding and lower branches to begin to taper the shape back to “conical”.

      Whenever you cut that much of the leader, whether it’s 2′ or 4′, the plant no longer has a leader. Instinctively it will try to establish another dominant stem to take the lead. Since you’re trying to “stunt” the plant and not let it get too much taller, (a difficult task I might add) you will from this point on concentrate annual pruning at the top to continue the “stunting” effort.

      Likewise, you’ll have to be diligent with pruning on the sides to try and keep the plant contained.

      You can prune now.

    25. Caroline Says:

      I made a big mistake and cut the main leader too short in our 5′-6′ green giants. The leader has now stopped growing in about 5 of the trees. 2 or 3 side leaders has started to grow. Should I cut all but one new side leader or leave the tree alone. The one good thing is the trees did get fuller but does not have the pyramid shape.

      Thank you

    26. Roger Says:

      You’re exactly right in selecting one of the stronger shoots and allowing that one to dominate. Simply remove or prune back the others to suppress dominance and restore the pyramidal shape.

      I’ll bet they’ll be fine. You say they’re otherwise healthy — and if so, these plants will quickly want to resume their natural growth, i.e. single-stem pyramidal.

    27. Angela Says:

      I planted some green giant arborvitaes last year. They grew fine all summer. They are only about 1 1/2 feet tall. This spring they are brown. Will they turn green?

    28. Roger Says:

      If they’re completely brown it’s likely they’re dead. You can scratch the stems and see if there’s any green, but I doubt it.

    29. Joan Says:

      We just planted a long row of green giants. Some are about three feet tall and have no apparent central leader. Do we need to do something to encourage a leader?

    30. Roger Says:

      There are certainly ‘Green Giants’ out there with more than one central leader, but it’s better for the plant (long-term) to have one central leader.

      Since your plants are only 3′ tall it’s still possible to select the strongest leader and prune out the other(s). Yes, it’s likely to look drastic at first, but they’re so young they’ll have no trouble recovering.

    31. Barry Says:

      Thank you so much for the articles. I recently started a small tree farm with my first specimens being 400 green giants. I read in one of the earlier replies that you recommend mulch. I have access to rough chopped hardwood mulch. I have read in other forums to mulch about four inches keeping it somewhat away from the trunk. What are your thoughts? Thanks in advance for your reply.

    32. Roger Says:

      Mulching would be a great idea for the ‘Green Giants’. Just make sure the mulch you’re getting has aged properly.

      Here’s an article on mulch with some more helpful points. In the article I say 2 to 3 inches. In your nursery situation you could lean more towards a “heavy 3 inches,” but take care near the base and trunk of the plants. (See article)

    33. Saul Says:

      Hi Roger,
      We recently had 5 Green Giants planted, close to 7′ tall each. Each tree has a central leader at the top of the tree. But in the case of one tree, there is a secondary trunk. It has been pruned back, but this trunk is pretty thick and looks like it goes all the way down into the ground/root ball. I think it would be good for the tree’s health and looks to have a single trunk with single leader. Would you recommend cutting off this secondary trunk at the ground?

      There’s also another tree that is quite full at the bottom, but again, it looks like there are numerous trunks (maybe five or so fairly thick ones) coming from the ground or maybe right above the ground in this case. Should I try to cut these away over time leaving just a single central trunk? Thanks for the help.

    34. Roger Says:

      There’s no question a single leader is more desirable for ‘Green Giants’.

      What makes the decision to remove some (leaders) to retain “one” a bit challenging is the current size of your plant(s). And not from a plant health standpoint, because the plant will ultimately recover, but from an aesthetic standpoint.

      At 7′ tall you will probably notice a drastic change in appearance once you’ve done the corrective pruning — especially as compared to the others.

      If you do prune out the undesirable stems/leaders, make your cut(s) close to where the stems/trunks come together (at the base). And the cut should be at a slight angle — not straight across. Also, be extra careful not to cut into the nearby stem/trunk.

    35. Chase Says:

      Hi Roger, looks like you’ve answered similar questions so far but I want to be sure as to not hurt my trees.

      I have 3 out 4 large (10-12 ft) thujas with second trunks. The trees are still fairly full when I pull back the smaller trunks on them so astethically they
      will be fine and they appear to still be growing right now here in Virginia.
      Of the 3 trees, almost all fo them have a second trunk that is only a few inches to maybe a foot shorter than the main one or tallest one.

      Do you think it is ok for me to properly remove those second trunks at this time?


    36. Roger Says:

      If the arbs are ‘Green Giants’ then ideally they should be single-trunk plants.

      If you feel that aesthetically the look after removing the weaker leader will be OK, then by all means go ahead. And, of course, the plant will ultimately fill out and develop as it should.

      As I’ve mentioned to others, be careful when cutting that you don’t scar the other stem/trunk. And cut on a slight angle if possible.

    37. Kristine Says:

      Hi Roger,
      I have 11 western arborvitae that we planted about 6 years ago. Some get full sun and some are more shaded. The 3 that get the most sun and are the tallest recently started to look thin. It appears as though the needles on a lot of the middle branches on the inside of these 3 trees are falling off, while the ends are green and plush and show some green shoots. It’s been a very dry summer here, so I’m wondering if they could be just dry or are are growing so high that they are starting to thin out? Any advice would appreciated!

    38. Roger Says:

      The fact that the outer foliage is green and the interior is thinning could indicate the plant is dry (or drier than those in the shade).

      I’d begin a watering schedule of sorts, particularly for the 3 in full sun — but I’d include the others as well. Deep soaking waterings are best. So first wet the soil beneath the plants so it “accepts” the watering and the water does not run off. Then place the open end hose at the base (of each plant) and allow the hose to run at a slow trickle for a length of time — perhaps 40 minutes to one hour. (A soaker hose is an option as well) Maybe do this once or twice a week during the hot, dry months. Don’t let them go into the late fall and winter dry either.

      Being on the conservative side, I’d hold off pruning the larger 3 Arbs for this season. Let the plants recover this season and then prune them next year so they fill out a bit.

    39. Justin Says:

      I have 12-14′ arborvitia’s bordering my property line in the back yard. Unfortunately i need to put up a 6′ fence to keep my dogs in the back yard and off a leash. I need to cut in about a half foot on one side of the bush and trim 6 feet from the bottom up. To make room for the fence about 40′ down the property line. There are a few spots where thick branches will need cut back. By doing this will it kill the entire arborvitae. I dont care if its dead against the fence, since no one could see. Just worried about the lush green on the yard side. I plan on paying a lawncare company to do this. They appear very health and beautiful. Its a shame we have to butcher it that bad on one side. But it is necessary for the fence line. Any thoughts would be appreciated. Thanks

    40. Roger Says:

      You’re right in that the side against the fence will be gone, but that does not necessarily affect the look and health of the rest of the plant. Therefore, prune what you have to for the fence install.

      It’s hard to give exact advice w/o being there and seeing the situation. But on the backside, where the fence is going, that foliage will likely brown and die — we see this all the time.

    41. Heidi Says:

      Hi Roger,
      Can Green Giants be trimmed into a formal hedge shape like the red cedars can?

    42. Roger Says:

      It’s certainly possible to trim/shear Green Giants, but keep in mind that this plant aspires to grow quite large… and quickly. This will make it more of a challenge to keep the plant/hedge within a manageable size for a long period of time.

    43. Glen Schardine Says:

      I have what I believe is a Green Giant it’s 25 foot tall 7 foot across, it’s over grown the spot its in.
      The plant was a Arbor Day sapling our son planted 24
      years ago. My question is how do I go about starting a
      new plant off of the one i have.
      Any advice you can give would be appreciated.

    44. Roger Says:

      I’m not sure your plant is a ‘Green Giant’. The fact that it’s only 7′ wide at 25′ tall is not characteristic of ‘GG’.

      Regardless, it’s quite challenging to propagate woody plants like arborvitae. My last experience with plant propagation was in college — and that was 40 years ago! :-) But I looked up specifically the details of propagating ‘GG’ and here are the details.

      PROPAGATION for Arborvitae ‘Green Giant': Dormant seed lots have been encountered occasionally on which stratification in a moist medium at 34 to 41°F for 30 to 60 days stimulated prompt germination (variation among seed lots). Cuttings rooted well when taken in January. Best to collect cuttings after cold weather has set in. Raulston mentioned 95% rooting on December–January cuttings with 8000 ppm IBA talc and mist. With 25 clones that I collected, rooting averaged 88% when treated with 5000 ppm KIBA, 3 perlite:1 peat, bottom heat (70°F), and mist.

      Your best bet would be to find a supplier of “arborvitae liners”. These would be very young, rooted plants that are inexpensive. You can then plant them out in your yard or field — or even grow them on in pots for a couple of years. Try and “Google it” and I’m sure you’ll find suppliers/growers.

    45. Rob Says:

      I have a row of 30 green giants planted on 4′ centers as a privacy screen. They started as 5 1/2′ trees and many are now approaching 20 feet after 8 years. They are 10′ at the base. They get full sun and are very healthy. They have grown pretty tightly together and are super healthy. I think that 5 more feet of height is as tall as I’d like them to get. Should I be worried that their being so close together may begin to take a toll on them? If so is there a pruning strategy I should consider for their height and width? They really are spectacular. Thanks!

    46. Roger Says:

      Your ‘Green Giants’ are keeping to their name. :-)

      I’m glad they’re doing so well, but you’ll have a challenge to keep their height in check. I would begin pruning the tops to slow the plant down and also realize, from a practical sense, how tall you’re able to reach and maintain them.

      With regard to their 4′ spacing, it would have been better to have more space between them, but they should be able to coexist as a hedge with this spacing.

      There really is nothing to do (pruning or otherwise) to address this spacing. Transplanting is probably not an option because at this stage they’re likely grown together as a hedge. And already the growth between them has died off and become bare. Therefore, continue to maintain them as this “unit/hedge,” i.e. prune the sides and tops to keep them within bounds — as best as possible.

    47. Rob Says:

      Thanks Roger. They look very healthy and happy. My wife says don’t mess with success and leave them alone. Can I trim the sides vertically to make them more “hedge-like?” If so, when during the year?

      Also I’m about to put in another row elsewhere for screening again. I’m thinking to use 5′ centers this time. Is there any way to keep them to 12 – 15′ height? Thanks!

    48. Roger Says:

      I would prune the sides and top if you want to preserve the plants long-term. Without pruning they’ll continue to get larger — aspiring to their mature size. Again, they don’t call them ‘Green Giants’ for nothing. :-)

      Prune/trim them as a hedge, i.e. don’t try to separate and treat them as individual plants. On the sides (front & back of hedge) prune/trim so the plant is slightly wider at the base and tapering towards the top. Not only does this look correct, but it’s how the plant naturally wants to develop.

      I would prune the overall plants in the spring. There are stored foods in the current growth that the plant will utilize through the fall and winter. Next spring you can safely prune as the plant begins its new cycle.

      In the long-term it will be difficult to keep these plants 12-15′ in height. Diligent pruning will extend the time you can keep them at that height.

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