Troubleshooting
Million bells problems — and how to fix them
Million bells (Calibrachoa × hybrida) 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.
Iron/magnesium chlorosis (yellowing between veins)
The most common issue; caused by pH above 6.2, waterlogged roots, or insufficient feeding. Lower pH with ericaceous feed, improve drainage, and apply iron chelate or Epsom salt (magnesium sulphate) foliar spray.
Powdery mildew
White powdery coating appears on leaves in warm days/cool nights with high humidity. Increase air circulation, avoid wetting foliage, and treat with potassium bicarbonate or sulphur-based fungicide at first signs.
Vine weevil
Adult vine weevils notch leaf edges at night; larvae destroy roots in compost during late summer. Apply nematode treatment (Steinernema kraussei) to container compost in late August–September in UK conditions.
Prevent million bells problems before they start
Most million bells issues are care-mismatch, not bad luck. Dial in the basics:
Looking for million bells in general rather than its problems? Read the full million bells care guide — light, water, soil and feeding.
Million bells problems — FAQ
Why is my million bells iron/magnesium chlorosis (yellowing between veins)?
The most common issue; caused by pH above 6.2, waterlogged roots, or insufficient feeding. Lower pH with ericaceous feed, improve drainage, and apply iron chelate or Epsom salt (magnesium sulphate) foliar spray.
Why is my million bells powdery mildew?
White powdery coating appears on leaves in warm days/cool nights with high humidity. Increase air circulation, avoid wetting foliage, and treat with potassium bicarbonate or sulphur-based fungicide at first signs.
Why is my million bells vine weevil?
Adult vine weevils notch leaf edges at night; larvae destroy roots in compost during late summer. Apply nematode treatment (Steinernema kraussei) to container compost in late August–September in UK conditions.