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Western Red Cedar · Thuja plicata

Why are there spots on my Western Red Cedar?

It is less common for this plant to develop spots, which usually points to a fungal infection like cedar leaf blight. Check the foliage for small, discolored lesions that might be spreading across the branches.

spots on a plant
Photo: Scot Nelson, CC0

Check these first

  1. Inspect the undersides of the needles for tiny webbing.
  2. Check if the spots are concentrated on the lower, inner branches.
  3. Look for signs of moisture buildup or poor airflow.

Likely causes

  1. Cedar leaf blight

    Possible

    How to tell: You will see small brown or black spots on the needles that eventually cause them to drop. It often starts on the lower branches where air circulation is poor.

    What to do: Prune away the affected branches to stop the spread. Improve airflow around the tree by thinning out dense foliage. Apply a copper based fungicide if the infection is widespread.

  2. Spider mite damage

    Possible

    How to tell: Look for tiny yellow or bronze stippling on the needles that looks like small dots. You might also see fine webbing between the needles if you look closely.

    What to do: Spray the foliage with a strong stream of water to knock the mites off. Use insecticidal soap or neem oil once a week for 3 weeks to control the population.

Find out what's wrong with your western red cedar

The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

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When to worry

You should worry if the spots are spreading rapidly and causing significant needle drop. It is normal to see some minor browning on the very oldest interior needles during late summer.

Stopping it coming back

Keep the tree healthy by watering consistently and ensuring it has plenty of space for air to move through the branches.

Keep your western red cedar healthy from here

Save your plant in Pocket Botanist and you get care reminders timed for this plant, plus a care history that shows what worked. Identification and a health check are free.

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Questions people ask

Will the spotted needles turn green again?
No, once a needle has developed spots or turned brown, it will not recover. It is best to prune it off so the tree can focus energy on new growth.
Can I use a general fungicide?
Yes, a copper based fungicide is usually effective for fungal issues on cedars. Always follow the label instructions for the correct dilution.

More problems with Western Red Cedar

Back to the Western Red Cedar guide

This article was generated with AI from the plant’s care profile and is general information, not horticultural advice. Read about how we build these guides.