West Highland Flora

Japanese Knotweed

Fallopia japonica var japonica

Former names: Reynoutria japonica, Polygonum cuspidatum

Fallopia japonica

Photo Carl Farmer
8 Sep 2002 Portree, Skye

An invasive non-native species which forms dense vigorous stands obliterating the native vegetation.  Common close to habitation and sometimes well away from it.  A serious threat to coastal habitats in Argyll.

Plant c 2-3 m tall, forming dense thickets

ID: Upright bamboo-like stems with long spikes of small white flowers very numerous along the branches.  Leaves cut off square at broad base, continuing broad for most of their length and then curving in to pointed tip.

Other features: Stems usually reddish and zigzag.  All British plants are female as far as known, and their successful spread has been entirely due to vegetative propagation.  This plant is often sprayed with herbicide, so that dead or partly withered stands of it are a common sight.  But more frequently it is left to grow unchecked.


Fallopia japonica

Photo Carl Farmer
30 Sep 2001 Portree, Skye

The last of the flowers falling from the spikes
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