Invasives And Non Native Species

Monitoring of Treatment of INNS Plants, River AVON

Japanese knotweed, Fallopia japonica

Japanese Knotweed Image © GBNNSS

Short description of Fallopia japonica, Japanese knotweed
Herbaceous perennial, with stems typically about 2m tall and an extensive system of rhizomes. It has large, roughly triangular leaves with truncate (not cordate (heart-shaped)) bases.

Description of Fallopia japonica, Japanese knotweed status in GB
Japanese knotweed is an invasive non-native weed, mainly in urban areas where it is considered a nuisance in property development, because plants regrowing from rhizomes can come up through gaps in flooring in conservatories and patios.

Impacts summary: Fallopia japonica, Japanese knotweed
Possibly the most economically important invasive non-native species in GB, as eradication is required by law in property development sites and that can be expensive. It has only limited impact ecologically.

Habitat summary: Fallopia japonica, Japanese knotweed
Urban areas, river banks and waste ground, usually in full sunshine. It is not shade tolerant and does not persist in woods. Long established stands by rivers tend to have a similar vernal ground flora to W6 Alnus glutinosa woods, with F. japonica providing the canopy layer during the summer months.

Overview table

Environment: Terrestrial
Species status: Non-Native
Native range: Eastern Asia
Invasion pathway: Ornamental
Functional type: Land plant
Status in GB: Established
Status in England: Established
Status in Scotland: Established
Status in Wales: Established
Location of first record: Glamorgan
Date of first record: 1886