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:
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.