Pocket Botanist
Check these first
- Look under the leaves for slugs or slimy trails.
- Check if the leaves are staying wet for long periods after watering.
- Inspect the plant for any signs of small insects.
Likely causes
Slugs
PossibleHow to tell: You will see irregular holes or small spots on the tender foliage, often accompanied by slimy trails. Slugs are most active in the spring when the plant is young.
What to do: Handpick slugs off the plant in the early morning or evening. You can also place a shallow dish of beer near the base to trap them.
Fungal leaf spot
PossibleHow to tell: Small, dark, or water-soaked spots appear on the leaves, often with a yellow halo. This happens when the foliage stays wet for too long in stagnant air.
What to do: Improve air circulation around the plant by spacing it away from other foliage. Avoid overhead watering to keep the leaves dry.
Find out what's wrong with your great blue lobelia
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 or causing the leaves to drop. A few small spots are usually manageable with better care.
Stopping it coming back
Water at the base of the plant rather than over the leaves. Keep the area around the plant clean and free of debris where slugs might hide.
Great blue lobelia: spots? Check yours with a photo
Every plant is a little different. Take a photo of your great blue lobelia 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
- Are these spots contagious to my other plants?
- If the spots are fungal, they can spread through water splashes. Isolate the affected plant until you are sure the issue is resolved.
- Can I use a fungicide for the spots?
- You can use a copper-based fungicide if the spots are clearly fungal. Always follow the label instructions carefully for the best results.
Guides to these causes
More problems with Great blue lobelia
Back to the Great blue lobelia 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.