Pocket Botanist
Check these first
- Inspect the undersides of the leaves for aphids.
- Feel the soil moisture 3 inches down.
- Check for signs of wilting or dry leaf edges.
Likely causes
Aphids
Most likelyHow to tell: You will see small, soft bodied insects on the undersides of leaves and a sticky substance called honeydew on the foliage. The leaves often curl or pucker as the insects feed on the sap.
What to do: Spray the leaves with a strong stream of water to knock the aphids off. If the infestation is heavy, apply insecticidal soap according to the label instructions. Repeat the treatment every 5 to 7 days until they are gone.
Drought Stress
PossibleHow to tell: The leaves look dry and curl inward to conserve moisture during hot, rainless periods. The edges may also turn brown and brittle.
What to do: Deeply water the tree at the base every 7 to 14 days during dry spells. Ensure the water reaches 12 to 18 inches into the soil. Apply a 3 inch layer of mulch around the base to help hold moisture in.
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 curling is accompanied by significant branch dieback, which could indicate a more serious health issue. Minor curling during a heatwave is often just the tree protecting itself.
Stopping it coming back
Keep your tree healthy with consistent watering during its first few years and monitor for pests early in the season.
Black Walnut: curling leaves? 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
- Will curling leaves kill my black walnut?
- Usually no, as long as the cause is addressed quickly. Most trees recover once the pests are removed or the soil moisture is balanced.
- Should I prune off the curled leaves?
- There is no need to prune them unless they are heavily infested with pests. The tree still uses those leaves to produce energy.
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.