Japanese knotweed Reynoutria japonica


Japanese knotweed is a fast-growing perennial herb in the family Polygonaceae. It forms dense stands which may reach up to 3 m tall. In its native habitat in Japan, it usually grows only 0,3 to 1,5 m in height.

Japanese knotweed thrives in a wide range of habitats. It requires light to grow and, therefore, it favors sunny habitats such as riversides, landfills and along roads and railways. It also grows in semi-shaded places such as forest clearings and edges, but rarely in forest. It also thrives on clayey and very barren habitats, and it is not demanding on soil acidity.

Source: FinBIF species descriptions
Description text authors:

Ryttäri, T. SYKE. Updated by Luke 2023.

CC BY 4.0

The map represents observations of this taxon, but it may not be used as a distribution map.

  • Total squares
FinBIF master checklist
Scientific name
Reynoutria japonica
Vernacular names
  • japanintatar (Finnish)
  • parkslide (Swedish)
  • Japanese knotweed (English)
Taxon rank
Occurrence in Finland
Collected from Finland
Status in Finland
  • TNV - alien, new, resident
  • 3 - spreading in the wild; completely of cultivated origin
This species is invasive
Regulatory Status
  • Finland’s National Strategy on Invasive Alien Species (GR 2012) ?
  • Government Decree on Managing the Risk Caused by Alien Species (704/2019, VN 912/2023) ?
Finnish Regional Red List Category
  • 2019 NA – Not Applicable
  • 2010 NA – Not Applicable
  • Pertti Uotila
DNA barcode sequences
Reynoutria japonica
3 public records
Fallopia japonica
93 public records
Informal groups
  • Vascular plants