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Slender St. John's Wort · Hypericum pulchrum

Why does my Slender St. John's Wort have spots on its leaves?

Spots on your Slender St. John's Wort are usually a sign of a fungal infection, often caused by high humidity or poor airflow. Check the undersides of the leaves for rust colored spores to confirm the issue.

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spots on a plant
Photo: Scot Nelson, CC0

Check these first

  1. Inspect the undersides of the leaves for orange or brown dust.
  2. Check if the plant is crowded by other foliage.
  3. Feel the soil to see if it stays soggy for too long.

Likely causes

  1. Rust fungus

    Most likely

    How to tell: You will see small, raised orange or brown pustules on the undersides of the leaves. The foliage may eventually yellow and drop off.

    What to do: Remove and destroy all infected leaves immediately to stop the spread. Improve air circulation around the plant by spacing it further from others. Avoid overhead watering to keep the foliage dry.

  2. Leaf spot disease

    Possible

    How to tell: Dark brown or black circular spots appear on the leaves, sometimes with a yellow halo. These spots often grow larger during wet weather.

    What to do: Prune away the most affected stems to reduce the fungal load. Apply a copper based fungicide if the infection persists. Ensure the plant is in a spot with good morning sun to dry off dew quickly.

Leaf spots on other plants

Find out what's wrong with your slender st. john's wort

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 spots are spreading rapidly across the entire plant or causing significant leaf loss. A few isolated spots are normal in very humid summers.

Stopping it coming back

Water only at the base of the plant and ensure it has plenty of space for air to move around the stems.

Slender St. John's Wort: spots? Check yours with a photo

Every plant is a little different. Take a photo of your slender st. john's wort 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

Can I save leaves that have spots?
It is best to remove spotted leaves as they will not heal and can spread spores to healthy parts of the plant.
Does this mean my plant will die?
Not necessarily, but it needs prompt attention. If you catch it early and improve the environment, the plant will recover.

Guides to these causes

More problems with Slender St. John's Wort

Back to the Slender St. John's Wort 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.