Pocket Botanist
Check these first
- Inspect the undersides of the leaves for orange dust.
- Check if the plant is crowded by other shrubs.
- Feel the soil to see if it stays wet for too long.
Likely causes
Rust fungus
Most likelyHow to tell: You will see small orange or brown spots on the undersides of the leaves. The foliage may eventually yellow and drop off.
What to do: Prune away all infected foliage immediately to stop the spread. Dispose of the clippings in the trash, not your compost pile. Apply a copper based fungicide if the infection is widespread.
Leaf spot disease
PossibleHow to tell: These spots are usually dark brown or black with a yellow halo around them. They often appear after periods of high humidity or heavy rain.
What to do: Remove affected leaves and improve air circulation around the plant. Avoid overhead watering to keep the foliage dry.
Find out what's wrong with your st. john's wort
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 cover more than half the plant or if the stems start to die back. A few spots here and there are common during wet seasons.
Stopping it coming back
Water at the base of the plant to keep leaves dry and ensure your St. John's wort has plenty of space for airflow.
St. John's wort: spots? Check yours with a photo
Every plant is a little different. Take a photo of your st. john's wort 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
- Will these spots kill my plant?
- Usually not, but they can weaken it significantly. Treating it early helps the plant recover faster.
- Should I use a fungicide?
- Only if pruning the infected parts does not stop the spread. Always follow the label instructions carefully.
Guides to these causes
More problems with St. John's wort
- Why is my St. John's wort looking so leggy?
- Why is my St. John's wort suffering from root rot?
- Why is my St. John's wort not flowering?
- Why are my St. John's wort leaves turning yellow?
- Why does my St. John's wort have brown leaf tips?
- Why is my St. John's wort drooping?
- What are the bugs on my St. John's wort?
Back to the St. John's wort 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.