Troubleshooting
Bachelor's button problems — and how to fix them
Bachelor's button (Centaurea cyanus) 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.
Powdery mildew
White powdery coating on leaves in warm, humid, low-airflow conditions. Improve spacing, avoid overhead watering, and remove affected foliage. Treat with a potassium bicarbonate spray if severe.
Aphid colonies
Clusters of green or black aphids on stem tips distort new growth. Knock off with a strong water jet or apply insecticidal soap. Ladybirds are effective biological controls.
Failure to flower
Caused by insufficient sun or overly rich soil. Move to a sunnier spot and avoid high-nitrogen feeds. Plants sown in autumn and overwintered flower earlier and more prolifically.
Prevent bachelor's button problems before they start
Most bachelor's button issues are care-mismatch, not bad luck. Dial in the basics:
- Common cornflower problems — the species this cultivar belongs to
- What's wrong with my plant? — the diagnosis apps compared
- Bachelor's button watering schedule
- Bachelor's button light requirements
- Best soil mix for bachelor's button
- Bachelor's button temperature & humidity
- Full bachelor's button care guide
Looking for bachelor's button in general rather than its problems? Read the full bachelor's button care guide — light, water, soil and feeding.
Bachelor's button problems — FAQ
Why is my bachelor's button powdery mildew?
White powdery coating on leaves in warm, humid, low-airflow conditions. Improve spacing, avoid overhead watering, and remove affected foliage. Treat with a potassium bicarbonate spray if severe.
Why is my bachelor's button aphid colonies?
Clusters of green or black aphids on stem tips distort new growth. Knock off with a strong water jet or apply insecticidal soap. Ladybirds are effective biological controls.
Why is my bachelor's button failure to flower?
Caused by insufficient sun or overly rich soil. Move to a sunnier spot and avoid high-nitrogen feeds. Plants sown in autumn and overwintered flower earlier and more prolifically.