Browning arborvitae

Asked July 19, 2020, 10:29 AM EDT

Good day. I have 2 very healthy arborvitae that I planted almost 16 years ago. My neighbor sprayed strong poison ivy killer 2-3 months ago near one of the trees. It is now browning and dry. There are some sprigs of bright green left though, but not many. We watered it and of course it has rained some. Can it be saved? What can I do to save this beautiful tree? Thanks

Rockland County New York

1 Response

I am so sorry and concerned not only for your poor trees, but on a higher level for the poisoning of the environment. I know this is alarming, but using toxic substances in the ground ends up going into our waterways. This impacts us all. Now that I got off my soapbox, I must say one more thing. The producers of these herbicide are indifferent to the environment contamination. I don't even want to imagine what health problems have arisen for humans, from food crop, and affects on beneficial pollinators like bees, to say the least!!!

From our recent research for our update NYBG libguides - While many conifers will not require any pruning, dead, damaged or diseased branches should be removed as soon as they are noticed, regardless of the season. See more below.

Here is an immediate management technique:

How to management the damage to trees in the landscape:

  • Damage can range from severe and possible plant death to the plant outgrowing the damage and recovering.

  • If it is known that the plant was sprayed by an herbicide, an immediate hosing of the foliage with water can reduce the damage. But, if the herbicide was absorbed by the plant it cannot be rinsed off.

  • Deeply water damaged trees and shrubs if needed.

  • Wait to see if the plant outgrows the damage. Damaged branches and stems can be pruned out but in some cases, the plant will have to be replaced.
https://hgic.clemson.edu/factsheet/herbicide-damage-to-landscape-plants/

Pruning your Arborvitae -

While many conifers will not require any pruning, dead, damaged or diseased branches should be removed as soon as they are noticed, regardless of the season. Arborvitae (Thuja) can create some new growth from lateral buds on young branches and, if necessary, can be moderately pruned before new growth appears, in late winter or early spring. Cut branches back to a side branch (lateral) and do not cut back more than ⅓ of the total length of the branch. This type of pruning will produce a fuller and more compact habit.

Most of the Cupressaceae family, including arborvitae, respond well to regular trimming of young growth and can be trimmed as formal hedges, provided that this more structured pruning is initiated from the start. They will not form new buds and growth from older wood.


Once arborvitae is mature in growth, pruning is best avoided unless essential. If, for instance, you remove a considerable amount from the tops of your trees to reduce an overgrown border, the top growth will not be replaced and the tops will remain relatively bald. Remember, arborvitae must be trained by pruning beginning when they are young and establishing a size limit annually. If you need to create a lower stand of attractive trees, replace them. The new, young trees can be pruned into a hedge at the height you wish.

Take care.