The Q&A Archives: Thuja emerald green

Question: 1) In the past 6 months, I have planted 20 thujas (10 gal). About 50% have developed a lot of brown needles, and 2 have died. There are no visible bugs, although I did spray just in case with a recommended spray...the browning occurred before the spraying. Do you have any suggestions as to cause and remedy?
Thank you. B

Answer: It's really difficult to diagnose a plant problem without actually seeing it. While thuja can develop spider mite problems, it isn't likely that yours have since they've been in the landscape only 6 months. A more likely cause of the foliage browning is a condition related to the soil or drainage. To be absolutely sure of the the cause of the browning, why not take a sample of the affected foliage to your local Cooperative Extension office? There's a plant problem diagnostic clinic there and trained volunteers will look at the samples under a microscope to determine just why they look abnormal. They'll also take a history of your plant; watering and fertilizing, exposure to sunshine, soil type, etc. Contact the Whatcom County Cooperative Extension at 360-676-6736; 1000 N. Forest St. in Bellingham.

Best wishes with your landscape!

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