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Boxwood Shrubs

Q.Boxwood Dormant Oil Spray

Zone 43015 | deanmorford50 added on April 26, 2020 | Answered

I recently treated my boxwoods with a horticultural oil spray. Now I am seeing significant yellowing of the leaves. Is it possible this yellowing is caused by the dormant oil spray? And will this cause significant, long term damage?

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Certified GKH Gardening Expert
Answered on April 27, 2020

Yes, this is very possible if this was done while it was sunny out. The instructions will suggest not spraying in sunlight for this reason. It is also best to test on a very small portion of the plant to ensure that there is no negative reaction. Depending on the strength of the dormant oil, it is possible that the mix was not diluted out enough, as well. Generally, this is not used on plants that do not experience a true dormancy, such as boxwoods, unless specifically stated for use outside of dormancy.

Unfortunately, the damage is done. Once the leaves fall off, it will likely recover on its own. If it doesn't recover as nice as you would like, then trimming it will help bring it back.

This article will help:


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