Troubleshooting
Blue Potato Bush problems — and how to fix them
Blue Potato Bush (Lycianthes rantonnetii) 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.
Whitefly
A frequent pest, especially under glass and in warm conditions. Fine webs and clouds of white insects on the undersides of leaves are diagnostic. Use yellow sticky traps, yellow-sticky sheet traps, or spray with insecticidal soap or pyrethrin-based spray. Biological control with Encarsia formosa works well under glass.
Frost damage
Tops are killed at about -2°C. In marginal zones (USDA 9), cut back in autumn, mulch roots heavily, and cover with fleece. Container plants should be moved into a frost-free conservatory or greenhouse for winter. Cut back hard in spring — recovery from the rootstock is vigorous.
Powdery mildew
Dry soil combined with humid stagnant air encourages powdery mildew on leaves and stems. Ensure good air circulation, water consistently at the root (not overhead), and treat early infections with a potassium bicarbonate or sulphur-based fungicide.
Prevent blue potato bush problems before they start
Most blue potato bush issues are care-mismatch, not bad luck. Dial in the basics:
Looking for blue potato bush in general rather than its problems? Read the full blue potato bush care guide — light, water, soil and feeding.
Blue Potato Bush problems — FAQ
Why is my blue potato bush whitefly?
A frequent pest, especially under glass and in warm conditions. Fine webs and clouds of white insects on the undersides of leaves are diagnostic. Use yellow sticky traps, yellow-sticky sheet traps, or spray with insecticidal soap or pyrethrin-based spray. Biological control with Encarsia formosa works well under glass.
Why is my blue potato bush frost damage?
Tops are killed at about -2°C. In marginal zones (USDA 9), cut back in autumn, mulch roots heavily, and cover with fleece. Container plants should be moved into a frost-free conservatory or greenhouse for winter. Cut back hard in spring — recovery from the rootstock is vigorous.
Why is my blue potato bush powdery mildew?
Dry soil combined with humid stagnant air encourages powdery mildew on leaves and stems. Ensure good air circulation, water consistently at the root (not overhead), and treat early infections with a potassium bicarbonate or sulphur-based fungicide.