Troubleshooting
Shrubby St. John's Wort problems — and how to fix them
Shrubby St. John's Wort (Hypericum prolificum) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Root rot
In poorly drained or heavy clay soils, roots may rot, causing yellowing leaves and dieback. Improve drainage before planting; avoid overwatering.
Leaf spots (Colletotrichum / Cercospora)
Fungal leaf spots can develop in humid conditions with poor air flow. Remove affected foliage, avoid overhead watering, and ensure adequate spacing.
Scale insects
Armored and soft scales may colonise stems, causing yellowing and sticky honeydew. Treat with horticultural oil during the dormant season or insecticidal soap on active infestations.
Prevent shrubby st. john's wort problems before they start
Most shrubby st. john's wort issues are care-mismatch, not bad luck. Dial in the basics:
Shrubby St. John's Wort problems — FAQ
Why is my shrubby st. john's wort root rot?
In poorly drained or heavy clay soils, roots may rot, causing yellowing leaves and dieback. Improve drainage before planting; avoid overwatering.
Why is my shrubby st. john's wort leaf spots (colletotrichum / cercospora)?
Fungal leaf spots can develop in humid conditions with poor air flow. Remove affected foliage, avoid overhead watering, and ensure adequate spacing.
Why is my shrubby st. john's wort scale insects?
Armored and soft scales may colonise stems, causing yellowing and sticky honeydew. Treat with horticultural oil during the dormant season or insecticidal soap on active infestations.