Should I prune off the curled leaves?

You do not need to prune them unless they are heavily infested with pests. The tree will eventually shed them naturally.

Are curled leaves a sign of Emerald Ash Borer?

Curling is not a primary symptom of Emerald Ash Borer, but the stress caused by the borer can make the tree look sickly. Look for canopy dieback and bark splitting instead.

Why are my Green Ash tree's leaves curling? Causes and fixes

Check these first

Examine the underside of curled leaves for aphids.
Observe if the leaves uncurl during the cooler morning hours.
Check for signs of Emerald Ash Borer, such as D shaped exit holes.

Likely causes

Aphid Infestation
Most likely
How to tell: You will see small, soft bodied insects on the undersides of leaves or sticky honeydew residue on the foliage. The leaves will appear curled and distorted as the insects feed.
What to do: Spray the foliage with a strong stream of water to dislodge the aphids. If the infestation is heavy, apply insecticidal soap according to the label instructions.
Heat Stress
Possible
How to tell: Leaves curl inward during the hottest part of the day to conserve moisture. The leaves usually look normal again in the evening or early morning.
What to do: Ensure the tree receives deep, thorough watering during dry spells. Apply a layer of wood chip mulch around the base to keep the root zone cool.

Curling leaves on other plants

Find out what's wrong with your green ash

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.

When to worry

Curling due to heat is a normal defense mechanism, but if the leaves stay curled and become brittle, the tree is under severe stress. If you see D shaped holes in the bark, contact an arborist immediately.

Stopping it coming back

Keep the tree healthy with consistent watering and monitor for early signs of pests. A well watered tree is much more resilient to heat and insect pressure.

Green Ash: curling leaves? Check yours with a photo

Every plant is a little different. Take a photo of your green ash 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

Should I prune off the curled leaves?: You do not need to prune them unless they are heavily infested with pests. The tree will eventually shed them naturally.
Are curled leaves a sign of Emerald Ash Borer?: Curling is not a primary symptom of Emerald Ash Borer, but the stress caused by the borer can make the tree look sickly. Look for canopy dieback and bark splitting instead.

Guides to these causes

Aphids

Why are my Green Ash tree's leaves curling?