Troubleshooting
Butterfly Bush 'Black Knight' problems — and how to fix them
Butterfly Bush 'Black Knight' (Buddleja davidii 'Black Knight') 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.
Failure to bloom
Usually too much shade or skipped pruning. Site in full sun and cut hard in early spring, since flowers form only on new wood.
Self-seeding and invasiveness
Seeds prolifically and is invasive in parts of the US and UK. Deadhead spent panicles before seed sets, or choose sterile cultivars where it is a problem.
Capsid bug or spider mite damage
Distorted shoot tips or fine mottling and webbing in hot dry spells. Encourage predators; hose down mites and tolerate minor cosmetic damage.
Powdery mildew
White coating on leaves in humid, crowded conditions. Improve airflow, avoid overhead watering and remove badly affected growth.
Prevent butterfly bush 'black knight' problems before they start
Most butterfly bush 'black knight' issues are care-mismatch, not bad luck. Dial in the basics:
- Common butterfly bush problems — the species this cultivar belongs to
- What's wrong with my plant? — the diagnosis apps compared
- Butterfly Bush 'Black Knight' watering schedule
- Butterfly Bush 'Black Knight' light requirements
- Best soil mix for butterfly bush 'black knight'
- Butterfly Bush 'Black Knight' temperature & humidity
- Full butterfly bush 'black knight' care guide
Looking for butterfly bush 'black knight' in general rather than its problems? Read the full butterfly bush 'black knight' care guide — light, water, soil and feeding.
Butterfly Bush 'Black Knight' problems — FAQ
Why is my butterfly bush 'black knight' failure to bloom?
Usually too much shade or skipped pruning. Site in full sun and cut hard in early spring, since flowers form only on new wood.
Why is my butterfly bush 'black knight' self-seeding and invasiveness?
Seeds prolifically and is invasive in parts of the US and UK. Deadhead spent panicles before seed sets, or choose sterile cultivars where it is a problem.
Why is my butterfly bush 'black knight' capsid bug or spider mite damage?
Distorted shoot tips or fine mottling and webbing in hot dry spells. Encourage predators; hose down mites and tolerate minor cosmetic damage.
Why is my butterfly bush 'black knight' powdery mildew?
White coating on leaves in humid, crowded conditions. Improve airflow, avoid overhead watering and remove badly affected growth.