Japanese knotweed – Reynoutria japonica
- Invasive alien species
Japanese knotweed is a fast-growing perennial herb. The stems reach up to 3 m in height. It is recorded as being smaller, 0.3-1.5 m in height, in its native range in Japan. Giant knotweed (Fallopia sachalinensis), closely related to Japanese knotweed, grows even taller, up to 4-5 metres, and its leaves are bigger, even over 40 cm in length. The characteristics of Bohemian knotweed (Fallopia × bohemica), a hybrid of Japanese knotweed and giant knotweed, lie somewhere between the stem species.Knotweeds’ stems are glabrous, hollow and slightly woody, often with reddish or reddish-brown flecks. The stems are annual and new ones emerge from the rhizome every year. Large knotweeds therefore produce plenty of litter.
Japanese knotweed thrives in a wide range of habitats. It requires light in order to grow and therefore favours sunny habitats. It also grows in semi-shady sites, such as forest openings and forest edges, but rarely in the actual forest.
- japanintatar (Finnish)
- vanligt parkslide (Swedish)
- Japanese knotweed (English)
- TNV - alien, new, resident
- 3 - spreading in the wild; completely of cultivated origin
|Establishment||Established|Government Decree on Managing the Risk Caused by Alien Species (704/2019) ? Finland’s National Strategy on Invasive Alien Species (GR 2012) ?
- 2019 NA – Not Applicable
- 2010 NA – Not Applicable
- Pertti Uotila
- Vascular plants