Diagnose cause of arborvitae death - Ask Extension
4 of my arborvitae died over the winter. The other 20 appear to be ok. The 4 are neighbors in the hedge. All were planted in the fall of 2019. We’d...
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Diagnose cause of arborvitae death #826415
Asked April 20, 2023, 12:57 AM EDT
4 of my arborvitae died over the winter. The other 20 appear to be ok. The 4 are neighbors in the hedge. All were planted in the fall of 2019. We’d like to figure out what did them in before replacing them.
Clackamas County Oregon
Expert Response
Thank you for your question, Laura. There are several factors which can cause arborvitae to brown and, in some cases, die. One is the combination of heat and inadequate water, especially in their early years. https://today.oregonstate.edu/news/arborvitae-stands-tall-easy-care-hedge
The second factor is an infection by one of several fungi, which may be either soil-borne or above ground. They are listed here: https://pnwhandbooks.org/plantdisease/host-and-disease-descriptions?title=arborvitae
I don't have enough information about your planting and watering schedule, and cannot diagnose a disease without a lab test.
As Dr. Bell indicates, drought stress may show up in some trees and not others. You can get a lab test done at the OSU Plant Clinic (https://bpp.oregonstate.edu/plant-clinic/submit-sample/how-submit-plant-materials), but you may just not have watered them enough in the past 4 summers. I can only speculate.
The second factor is an infection by one of several fungi, which may be either soil-borne or above ground. They are listed here: https://pnwhandbooks.org/plantdisease/host-and-disease-descriptions?title=arborvitae
I don't have enough information about your planting and watering schedule, and cannot diagnose a disease without a lab test.
As Dr. Bell indicates, drought stress may show up in some trees and not others. You can get a lab test done at the OSU Plant Clinic (https://bpp.oregonstate.edu/plant-clinic/submit-sample/how-submit-plant-materials), but you may just not have watered them enough in the past 4 summers. I can only speculate.
