Knowledgebase
Maintaining Thuja Green Giant at 15 feet high #872108
Asked June 07, 2024, 3:49 PM EDT
Washtenaw County Michigan
Expert Response
Hello
You can clip or shear them but if you cut into the bare wood trunk they may not fill in properly. ‘Topping’ cuts into the woody trunk and opens the plant to disease. However, there are examples of maintaining them at desired height successfully by pruning every year.
Now that they are there, try maintaining them at your desired height and width. Be sure the tops are slightly narrower than the bottoms so that the bottoms, where your visual screening occurs, doesn’t’ get shaded and begin to thin.
See the advice on pruning arbs here-
https://s3.wp.wsu.edu/uploads/sites/2076/2021/09/C111-Pruning-Evergreens-format-update-21.pdf
And shaping evergreens so the bottoms are not shaded, here—
https://extension.umd.edu/resource/pruning-shrubs-and-hedges-home-garden/
I have seen an example of arborvitae that are maintained at a static height by clipping them 2-3 times per year(the hedge I have seen is maintained as a topiary would be, clipped into a geometric rectangular shape)
There are arbs whose mature height is about 15 feet, should you end up having to replace yours. One popular arborvitae (Thuja occidentalis) is ‘Emerald Green,’ also known as ‘Smaragd’, which matures at about 15 feet tall by 4 feet wide.
Thanks for the reply. Right now the trees are planted 12 - 14 feet apart on center. Would adding adding another green giant in between the current trees, to make the spacing 6-8 feet on center, help keep their size down?
Regards,
Laura
Thanks. Can you share a picture or link of a thuja green giant hedge that is maintained at 15 or 20 feet high?
https://ag.umass.edu/home-lawn-garden/photos/trimming-arborvitae