Troubleshooting
PJM rhododendron problems — and how to fix them
PJM rhododendron (Rhododendron × 'PJM') 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.
Winter desiccation
In zones 4–5, cold drying winds combined with frozen soil prevent water uptake while evergreen leaves continue losing moisture, causing brown leaf margins or full leaf scorch. Apply an anti-desiccant spray in late November and shelter from prevailing winter winds.
Powdery mildew
White fungal coating on leaves in warm, dry summers with cool nights. Ensure good air circulation; the compact habit can trap humid air. Treat with a sulphur-based or potassium bicarbonate fungicide at first signs.
Root weevil damage
Irregular notching of leaf margins caused by adult vine/black vine weevils feeding at night. Grubs in the soil can severely damage roots of young or container-grown plants. Apply Steinernema nematodes in late summer to moist root zones.
Prevent pjm rhododendron problems before they start
Most pjm rhododendron issues are care-mismatch, not bad luck. Dial in the basics:
Looking for pjm rhododendron in general rather than its problems? Read the full pjm rhododendron care guide — light, water, soil and feeding.
PJM rhododendron problems — FAQ
Why is my pjm rhododendron winter desiccation?
In zones 4–5, cold drying winds combined with frozen soil prevent water uptake while evergreen leaves continue losing moisture, causing brown leaf margins or full leaf scorch. Apply an anti-desiccant spray in late November and shelter from prevailing winter winds.
Why is my pjm rhododendron powdery mildew?
White fungal coating on leaves in warm, dry summers with cool nights. Ensure good air circulation; the compact habit can trap humid air. Treat with a sulphur-based or potassium bicarbonate fungicide at first signs.
Why is my pjm rhododendron root weevil damage?
Irregular notching of leaf margins caused by adult vine/black vine weevils feeding at night. Grubs in the soil can severely damage roots of young or container-grown plants. Apply Steinernema nematodes in late summer to moist root zones.