Invasives And Non Native Species

Japanese knotweed, Fallopia japonica

Japanese Knotweed Image © GBNNSS

LAC actively spray to try to limit the spread of JapaneseKnotweed on the River Avon watercourse extending to the main burns in the River Avon system. This has some success but the spread of this highly invasive plant is extensive. Spraying is carried out in late August just before the plant dies back for the winter.

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 and 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.

Impact summary
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.

Typical habitat 
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.