Japanese Knotweed, Fallopia Japonica

A rhizomatous perennial plant which was introduced into Europe in the 18th century as an ornamental plant and also to provide ground cover and fodder. Since its introduction, it has thrived in the European climate and with no natural predators it has become a force to be reckoned with.

Reproduction is vegetative regeneration with fragments of rhizome as small as 0.7g being enough to give rise to a fresh plant. All European plants are female and because they don’t need male germination, we have no male plants in Europe. All reproduction is purely through cuttings being transported to new site areas.

The rhizome and root system can spread up to 7 metres in length and 3 metres in depth dependent on soil conditions. It can survive in water for some time and still be viable when in contact with soil.

It thrives on disturbance and has been spread by both natural and human activity. In river areas, high water picks up rhizome fragments and juvenile plants and deposits them further down stream to start new infestations. Fly tipping and careless transportation by humans is the largest means of the plant spreading.