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Lilac · Syringa vulgaris

Why does my common lilac have white spots on its leaves?

That white, dusty coating is almost certainly powdery mildew. It shows up when the weather is warm and humid, especially if there is poor airflow around your shrub.

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spots on a plant
Photo: Scot Nelson, CC0

Check these first

  1. Check if the white coating wipes off easily with your finger.
  2. Inspect the center of the shrub for dense, tangled branches.
  3. Look at the underside of the leaves for signs of insects.

Likely causes

  1. Powdery Mildew

    Most likely

    How to tell: You will see a white, floury substance covering the leaves and sometimes the stems. It usually starts in mid to late summer.

    What to do: Prune out crowded branches to improve air circulation. If the infection is heavy, apply a fungicide labeled for powdery mildew or a mix of one tablespoon of baking soda in a gallon of water.

  2. Cercospora Leaf Spot

    Possible

    How to tell: These appear as small, brown or gray spots with dark borders on the leaves. They often cause the leaf to yellow and drop prematurely.

    What to do: Rake up and destroy all fallen leaves in the autumn to stop the fungus from overwintering. Keep the foliage dry by watering only at the base of the plant.

Leaf spots on other plants

Find out what's wrong with your lilac

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

Powdery mildew is rarely fatal, but it looks unsightly. Worry if the leaves start turning brown and dropping early in the season.

Stopping it coming back

Plant your lilacs in full sun with plenty of space between them to ensure good airflow.

Lilac: spots? Check yours with a photo

Every plant is a little different. Take a photo of your lilac 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 powdery mildew kill my lilac?
Usually no. It is mostly a cosmetic issue that stresses the plant but rarely causes permanent damage.
Should I cut off all the spotted leaves?
You can remove heavily infected leaves to slow the spread, but do not strip the entire plant as it needs leaves to make energy.

Guides to these causes

More problems with Lilac

Back to the Lilac 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.