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Sweet Pea · Lathyrus odoratus

Why are there white spots on my sweet pea leaves?

Those white, dusty patches are likely powdery mildew, a common fungal issue for sweet peas. It thrives when the air is humid and the leaves stay wet for too long.

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spots on a plant
Photo: Scot Nelson, CC0

Check these first

  1. Check if the white spots rub off easily with your finger.
  2. Examine the plant for signs of poor air circulation.
  3. Look at the base of the plant to see if the soil is staying too wet.

Likely causes

  1. Powdery Mildew

    Most likely

    How to tell: You will see a white, floury coating on the surface of the leaves and stems. It usually starts on older leaves and spreads upward.

    What to do: Remove and destroy the most heavily infected leaves to stop the spread. Improve air circulation around your plants and avoid overhead watering to keep the foliage dry.

  2. Fungal Leaf Spot

    Possible

    How to tell: These appear as distinct brown or black spots with yellow halos on the leaves. They often occur during periods of heavy rain.

    What to do: Prune away affected foliage to improve airflow. Apply a copper based fungicide if the infection continues to spread across the plant.

Leaf spots on other plants

Find out what's wrong with your sweet pea

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

Treat this as soon as you see it, as powdery mildew spreads rapidly in warm, humid weather. If the entire plant is covered, it may be too late to save the foliage.

Stopping it coming back

Water only at the base of the plant to keep the leaves dry. Space your plants 6 to 10 inches apart to ensure good airflow.

Sweet Pea: spots? Check yours with a photo

Every plant is a little different. Take a photo of your sweet pea 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

Is powdery mildew harmful to me?
No, it is a plant specific fungus and will not harm humans or pets. However, it will eventually drain the energy from your sweet peas.
Should I throw away infected leaves?
Yes, do not put them in your compost pile. Bag them up and put them in the trash to prevent the spores from spreading to other plants.

Guides to these causes

More problems with Sweet Pea

Back to the Sweet Pea 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.