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Check these first
- Inspect the stems for fuzzy growth or visible spores.
- Check the water for foul odors or excessive algae buildup.
- Clear away any decaying plant matter from the surface of the water.
Likely causes
Fungal Leaf Spot
PossibleHow to tell: You will see small, dark, or discolored patches appearing on the green stems. These spots may grow larger or merge if the humidity remains too high without airflow.
What to do: Remove the affected stems immediately to prevent the spread of spores. Ensure the water in your pond or container is circulating or refreshed regularly. Avoid overhead watering that keeps the stems wet for extended periods.
Water Quality Issues
PossibleHow to tell: The stems might show yellow or brown spotting if the water has become too acidic or contains high levels of mineral buildup. This often happens in small, closed containers where evaporation concentrates salts.
What to do: Flush the container with fresh, clean water to dilute any mineral buildup. If you are using tap water, let it sit for 24 hours to allow chlorine to dissipate before adding it. Consider testing the water pH to ensure it stays near neutral.
Find out what's wrong with your water horsetail
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 spread rapidly to healthy stems or if the entire plant begins to collapse. It is normal for a few older stems to show minor wear as they age.
Stopping it coming back
Keep the water moving or refreshed often and ensure the plant has plenty of space for air to circulate around the stems.
Water horsetail: spots? Check yours with a photo
Every plant is a little different. Take a photo of your water horsetail 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
- Should I use a fungicide on my water horsetail?
- It is usually better to prune away the damaged stems and improve the water quality first. Chemical fungicides can be harmful to the aquatic life or beneficial bacteria in your pond.
- Can spots be caused by too much sun?
- While water horsetail loves full sun, extreme heat combined with very low water levels can cause stress that looks like spotting. Always keep the roots submerged to prevent heat stress.
Guides to these causes
More problems with Water horsetail
Back to the Water horsetail 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.