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Pruning guide · Herbaceous plant
Japanese knotweed: when and how to prune
Reynoutria japonica
Japanese knotweed is best pruned in April–October.
| Pruning months | April–October |
|---|---|
| Flowering | August–October |
| Native to Belgium | No, an invasive alien species |
Japanese knotweed: when to prune it?
From April to October, every 2–3 weeks: not to look after the plant, but to exhaust it.
What else to prune in those months? April · May · June · July · August · September · October
Japanese knotweed: how to prune it?
- Cut or mow the stems as low as possible as soon as they reach 20–30 cm.
- Pick up every piece: even a stem fragment with a node can root on moist soil.
- Do not use a flail mower or shredder: they scatter small fragments over a large area.
- Clean the mower, shoes and tyres before you leave the site.
How much to cut, and how often?
- One pruning period a year: April–October.
What does it mean for wildlife?
- Spreads in the wild at the expense of native species. Better removed than pruned, and never dump the prunings in the countryside.
Caution: Occasional cutting does not help and actually triggers extra shoots: only frequent cutting, kept up for years, wears it out.
Nearby: related pruning guides
Plant profile: Japanese knotweed · Pruning calendar and basic rules
This guide is compiled from the Bladwijzer plant profile and pruning calendar.