Troubleshooting
Black Knight Butterfly Bush problems — and how to fix them
Black Knight Butterfly Bush (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.
Invasive self-seeding
Prolific seed producer; deadhead promptly after flowering to prevent unwanted seedlings in borders and on walls.
Buddleja weevil (Mesagroicus obscurus)
Notched leaf margins; chemical treatment is rarely warranted for healthy established shrubs.
Phytophthora root rot
Occurs in waterlogged soils; improve drainage and avoid overwatering. Remove severely affected plants.
Capsid bugs
Cause puckered, distorted shoot tips in summer; pick off affected growth or treat with contact insecticide.
Frost die-back
Stems can die back in harsh winters but regrow vigorously from the base; hard pruning to 30 cm in late winter encourages the best flowering wood.
Prevent black knight butterfly bush problems before they start
Most black knight butterfly bush 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
- Black Knight Butterfly Bush watering schedule
- Black Knight Butterfly Bush light requirements
- Best soil mix for black knight butterfly bush
- Black Knight Butterfly Bush temperature & humidity
- Full black knight butterfly bush care guide
Looking for black knight butterfly bush in general rather than its problems? Read the full black knight butterfly bush care guide — light, water, soil and feeding.
Black Knight Butterfly Bush problems — FAQ
Why is my black knight butterfly bush invasive self-seeding?
Prolific seed producer; deadhead promptly after flowering to prevent unwanted seedlings in borders and on walls.
Why is my black knight butterfly bush buddleja weevil (mesagroicus obscurus)?
Notched leaf margins; chemical treatment is rarely warranted for healthy established shrubs.
Why is my black knight butterfly bush phytophthora root rot?
Occurs in waterlogged soils; improve drainage and avoid overwatering. Remove severely affected plants.
Why is my black knight butterfly bush capsid bugs?
Cause puckered, distorted shoot tips in summer; pick off affected growth or treat with contact insecticide.
Why is my black knight butterfly bush frost die-back?
Stems can die back in harsh winters but regrow vigorously from the base; hard pruning to 30 cm in late winter encourages the best flowering wood.