Excelsa Cedar turning brown on bottom? - Ask Extension
Hello. 4 years ago, I planted a tree called Thuja plicata Excelsa which looks like a smaller version of the red western cedar. The tree is a fast grow...
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Excelsa Cedar turning brown on bottom? #775119
Asked October 12, 2021, 12:19 PM EDT
Hello. 4 years ago, I planted a tree called Thuja plicata Excelsa which looks like a smaller version of the red western cedar. The tree is a fast grower. At the tail end of summer and beginning of fall I noticed that some of the bottom branches started turning a bronze color. Now even more branches are turning this color. We live with clay soils and that tree is planted on a slight slope. During the summer, the cedar was watered once a week. One day however, I accidentally left the water running on the tree for over an hour. It was a few weeks after that when I noticed the beginning of the discolored branches on the bottom. Now I fear that my cedar has some sort of root rot, or is this a natural fall shedding ? It is planted next to a row of Arborvitae. Do you know what has caused this discoloration, and if so, should I be cutting these dying branches off the bottom? And lastly, do you think whatever it is could spread to the Arborvitae. I have attached 3 photos of the cedar tree. Any info you could send would be greatly appreciated.
Lane County Oregon
Expert Response
Your images show a few bottom branches of a western red cedar that have died back. The branches have tuned tan or straw colored and will not be alive again. Those branches can be pruned off anytime. It is not clear if other branches have turned an off green or yellow green color in the smaller image. I would be more concerned if that were the case. By cutting out the dead branches you may discover other things going on near the base of the tree that could explain the problem. The causes are too numerous to list here. Just have a look at the base of the tree to see what might be going on. (Why is that board sticking out from under there? What is up with all those cement blocks on the other side of the fence, etc....?)
Root rot is a possibility but those are few. It does not look like your yard is in a new development which might indicated Armilaria root rot. You can check here for more info:
https://pnwhandbooks.org/plantdisease/host-disease/cedar-all-kinds-root-rot-armillaria
Leaving the water on for extended periods could encourage Phytophthora root rot but that is not certain based on the images. More extensive damage might be explained by a root rot. The root rots could move to the other conifers but for now I would not worry about that. You read a little more about these diseases here: https://pnwhandbooks.org/plantdisease/host-disease/cedar-port-orford-chamaecyparis-lawsoniana-root-rot
And just cover the bases it is not drought related as we generally see the tops of trees die back from those causes.
Root rot is a possibility but those are few. It does not look like your yard is in a new development which might indicated Armilaria root rot. You can check here for more info:
https://pnwhandbooks.org/plantdisease/host-disease/cedar-all-kinds-root-rot-armillaria
Leaving the water on for extended periods could encourage Phytophthora root rot but that is not certain based on the images. More extensive damage might be explained by a root rot. The root rots could move to the other conifers but for now I would not worry about that. You read a little more about these diseases here: https://pnwhandbooks.org/plantdisease/host-disease/cedar-port-orford-chamaecyparis-lawsoniana-root-rot
And just cover the bases it is not drought related as we generally see the tops of trees die back from those causes.
