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Black Walnut · Juglans nigra

How do I fix root rot in my black walnut?

It is less common for a black walnut to develop root rot unless it is planted in heavy, waterlogged soil. Check the drainage and the smell of the soil first.

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root rot on a plant
Photo: Ninjatacoshell, CC BY-SA 3.0

Check these first

  1. Smell the soil near the base of the tree.
  2. Check if the ground stays wet for long periods.
  3. Look for dark lesions on the trunk near the soil line.

Likely causes

  1. Poor Drainage

    Possible

    How to tell: The soil remains soggy and smells sour or like rotten eggs. The tree shows stunted growth and yellowing leaves.

    What to do: Improve the soil drainage by amending the surrounding area with organic matter. Avoid adding more water until the soil is dry to the touch.

  2. Phytophthora Root Rot

    Possible

    How to tell: The tree declines slowly with thinning foliage and dark, sunken lesions near the base of the trunk. This is caused by water molds in saturated soil.

    What to do: Stop all irrigation immediately to let the roots breathe. In severe cases, you may need to install a drainage system to move water away from the root zone.

Root rot in other plants

Find out what's wrong with your black walnut

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

Worry if the trunk base feels soft or if the tree is losing large amounts of leaves. It is normal for the soil to be damp after a heavy rainstorm.

Stopping it coming back

Plant your walnut in well draining soil and avoid overwatering. Ensure the root flare is visible and not buried under mulch.

Black Walnut: root rot? Check yours with a photo

Every plant is a little different. Take a photo of your black walnut and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.

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Questions people ask

Can I treat root rot with chemicals?
Fungicides are rarely effective for established trees. Improving the soil environment is the best path forward.
Is my tree going to die?
If the rot is caught early and drainage is improved, the tree can recover. If the trunk is already rotting, the prognosis is poor.

Guides to these causes

More problems with Black Walnut

Back to the Black Walnut guide

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