Troubleshooting
Canna 'Pretoria' problems — and how to fix them
Canna 'Pretoria' (Canna 'Pretoria') 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.
Canna leaf roller
Caterpillars roll and feed inside the leaves, causing ragged damage. Remove affected leaves and caterpillars by hand; use Bacillus thuringiensis as a biological control.
Spider mites in dry conditions
Fine webbing and mottled foliage indicate spider mites. Increase humidity, wash foliage, and apply a suitable miticide if infestation is heavy.
Viral mosaic
Canna yellow stripe virus causes mosaic discolouration on leaves. Remove and destroy affected plants; there is no cure. Buy from reputable, virus-indexed sources.
Frost damage
Cannas are not frost hardy in most of the UK and cooler US regions. Lift rhizomes in autumn after the first frost and store in dry compost in a frost-free location.
Bacterial bud rot
Young buds can blacken and rot in wet weather. Improve air circulation and avoid overhead watering to reduce this risk.
Prevent canna 'pretoria' problems before they start
Most canna 'pretoria' issues are care-mismatch, not bad luck. Dial in the basics:
Canna 'Pretoria' problems — FAQ
Why is my canna 'pretoria' canna leaf roller?
Caterpillars roll and feed inside the leaves, causing ragged damage. Remove affected leaves and caterpillars by hand; use Bacillus thuringiensis as a biological control.
Why is my canna 'pretoria' spider mites in dry conditions?
Fine webbing and mottled foliage indicate spider mites. Increase humidity, wash foliage, and apply a suitable miticide if infestation is heavy.
Why is my canna 'pretoria' viral mosaic?
Canna yellow stripe virus causes mosaic discolouration on leaves. Remove and destroy affected plants; there is no cure. Buy from reputable, virus-indexed sources.
Why is my canna 'pretoria' frost damage?
Cannas are not frost hardy in most of the UK and cooler US regions. Lift rhizomes in autumn after the first frost and store in dry compost in a frost-free location.
Why is my canna 'pretoria' bacterial bud rot?
Young buds can blacken and rot in wet weather. Improve air circulation and avoid overhead watering to reduce this risk.