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Bigleaf Hydrangea · Hydrangea

Why are there spots on my hydrangea leaves?

Spots on hydrangea leaves are often a sign of fungal issues or pest activity. Check the undersides of the leaves to see if you can spot any insects or fuzzy growth.

spots on a plant
Photo: Scot Nelson, CC0

Check these first

  1. Look for white dust on the leaf surfaces.
  2. Inspect the undersides of leaves for tiny insects.
  3. Check if the plant is crowded by other foliage.

Likely causes

  1. Powdery mildew

    Most likely

    How to tell: A white, dusty fungal growth appears on the surface of the leaves. It thrives in high humidity and poor air circulation.

    What to do: Improve air circulation around the plant by spacing it away from others. Apply a neem oil spray or a fungicide labeled for powdery mildew.

  2. Aphids

    Possible

    How to tell: It is less common for this plant, but usually caused by high nitrogen fertilizer use. You will see small clusters of insects on new growth and sticky residue on the leaves.

    What to do: Wash the aphids off with a gentle stream of water from a hose. Use an insecticidal soap spray once a week until the pests are gone.

Find out what's wrong with your bigleaf hydrangea

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

If the spots are spreading rapidly and causing leaves to curl or drop, treat the plant immediately. A few small spots are normal as the plant ages.

Stopping it coming back

Water at the base of the plant to keep leaves dry and ensure good airflow between stems.

Keep your bigleaf hydrangea 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

Are these spots contagious to my other plants?
Yes, fungal spores like powdery mildew can easily spread to nearby plants. Isolate your hydrangea until the spots are cleared up.
Will the spots go away after treatment?
The existing spots will not disappear, but treatment will stop them from spreading. New growth should emerge healthy and spot free.

More problems with Bigleaf Hydrangea

Back to the Bigleaf Hydrangea 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.