Pocket Botanist
Check these first
- Check the undersides of the leaves for orange spots.
- Look for white dust on the top of the leaves.
- Ensure the plant is not crowded by other pots.
Likely causes
Mint rust
Most likelyHow to tell: You see orange or reddish pustules on the undersides of the leaves.
What to do: Remove and destroy all affected leaves immediately. Improve air circulation by spacing your plants further apart.
Powdery mildew
PossibleHow to tell: A white, dusty coating appears on the surface of the leaves.
What to do: Wipe the leaves with a mixture of water and a tiny bit of baking soda. Ensure the plant is in a spot with good airflow.
Find out what's wrong with your spearmint
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
Rust is serious and can spread to other plants quickly. If the spots cover most of the foliage, it is best to prune the plant back hard or discard it.
Stopping it coming back
Water at the base of the plant to keep the leaves dry, and provide plenty of room for air to move around the stems.
Spearmint: spots? Check yours with a photo
Every plant is a little different. Take a photo of your spearmint 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
- Should I throw away the whole plant if it has rust?
- If the infection is severe, it is safer to discard the plant to protect your other herbs. If it is just a few leaves, prune them off and monitor closely.
- Does humidity cause these spots?
- Yes, high humidity combined with poor airflow creates the perfect environment for fungal spores to grow.
Guides to these causes
More problems with Spearmint
- Why are my spearmint leaves turning yellow?
- How do I get rid of pests on my spearmint?
- Why is my spearmint plant drooping?
- Why is my spearmint growing tall and leggy?
- Why are my spearmint leaves turning brown at the tips?
- Why is my spearmint losing its leaves?
- Why is my spearmint plant wilting and rotting?
- Why are my spearmint leaves curling?
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.