Pocket Botanist
Check these first
- Inspect the undersides of the leaves for aphids.
- Check if the leaves are crowded by other plants.
- Look for any slimy residue on the leaves.
Likely causes
Aphid damage
Most likelyHow to tell: You see tiny clusters of green or black insects on the new growth or flower spikes. The spots are often small yellow or brown marks where the aphids have been feeding.
What to do: Gently spray the leaves with a stream of water to knock the aphids off. If they persist, wipe the leaves with a damp cloth or use an insecticidal soap safe for aquatic plants.
Fungal leaf spot
PossibleHow to tell: Small brown or black spots appear on the leaves, sometimes with a yellow halo around them. This happens when the foliage stays wet and the air circulation is poor.
What to do: Remove the affected leaves to stop the spread. Ensure the plant has enough space and is not crowded by other plants. Improve air movement around the plant if possible.
Find out what's wrong with your water smartweed
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.
Scan with your phone's camera to get the app
Or go to pocketbotanist.app/get on your phone
When to worry
Worry if the spots are spreading quickly or causing the leaves to rot. A few small marks are usually just minor cosmetic damage.
Stopping it coming back
Keep the plant in a spot with good airflow and check for aphids every time you refresh the water.
Water smartweed: spots? Check yours with a photo
Every plant is a little different. Take a photo of your water smartweed 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.
Scan with your phone's camera to get the app
Or go to pocketbotanist.app/get on your phone
Get the app · Or check it from a photo now, free
Questions people ask
- Are these spots a sign of a disease?
- They can be, but they are often just signs of aphid feeding. Check for insects before assuming it is a fungal issue.
- Can I use fungicide on my water smartweed?
- Avoid chemical fungicides, as they can harm the water quality and any aquatic life in the container. Stick to physical removal of damaged leaves.
Guides to these causes
More problems with water smartweed
Back to the water smartweed 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.