Pocket Botanist
Check these first
- Inspect the undersides of the leaves for orange dust.
- Check if the plant is crowded by other vegetation.
- Feel the leaves to see if they stay wet for hours after watering.
Likely causes
Rust Fungus
Most likelyHow to tell: You will see small, raised orange or reddish brown pustules on the leaf surfaces. These often appear after periods of high humidity or poor airflow.
What to do: Snip off the affected leaves immediately to stop the spread. Improve air circulation around the plant by spacing it further from others and avoid getting water on the foliage when you irrigate.
Leaf Spot Disease
PossibleHow to tell: These spots are usually darker, often brown or black, and may have a yellow halo around them. They tend to grow larger over time if the plant stays wet.
What to do: Remove infected foliage and dispose of it in the trash, not your compost. Keep the soil moist but ensure the surface dries slightly between waterings to reduce fungal pressure.
Find out what's wrong with your marsh willowherb
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 cover more than half of the leaves, the plant may struggle to photosynthesize. A few small spots are common in wild settings but should be managed in a garden.
Stopping it coming back
Water at the base of the plant to keep leaves dry and ensure there is plenty of space for air to move between stems.
Marsh willowherb: spots? Check yours with a photo
Every plant is a little different. Take a photo of your marsh willowherb 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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Or go to pocketbotanist.app/get on your phone
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Questions people ask
- Can I save a leaf with spots?
- It is better to remove it. Once the fungus takes hold, it is hard to stop, and removing the leaf prevents it from spreading to healthy parts of the plant.
- Will this kill my plant?
- Usually no, but it weakens the plant significantly. If left untreated, the plant may lose so many leaves that it stops growing or fails to bloom.
Guides to these causes
More problems with Marsh willowherb
- Why is my Marsh willowherb drooping?
- Why is my Marsh willowherb growing so leggy?
- Why are my Marsh willowherb leaves turning yellow?
- Why are my Marsh willowherb's leaf tips turning brown?
- Why is my Marsh willowherb dropping leaves?
- Why is my marsh willowherb not flowering?
- Why does my marsh willowherb have pests?
- Why are my marsh willowherb leaves curling?
Back to the Marsh willowherb 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.