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Japanese knotweed, sometimes known locally as donkey rhubarb, (scientific name Fallopia japonica) was introduced to the UK in the mid nineteenth century as an ornamental plant. Since then it has become a serious problem in a range of habitats, particularly roadsides, riverbanks and derelict land, displacing native flora and causing structural damage.
In the UK, although Japanese knotweed plants produce seeds, these are rarely viable. Therefore spread is by vegetative means, either by rhizome (root) fragments, or by crown (base of the stem) and stem segments.
The majority of Japanese knotweed has been spread by riverbank erosion, and by mans' activities, such as fly-tipping garden waste and moving contaminated soil. Mechanical flails and mowers will also spread the plant.
In Cornwall Japanese knotweed has become widespread. Many watercourses are choked with it and large areas of derelict land, wasteland, roadside verges and hedges have become infested. It is a significant problem making it difficult to restore or develop land, displacing important native flora, blocking visibility and causing physical damage to roads and property. Because of its highly invasive nature and the difficulties in controlling it, it has become an expensive weed to manage.
Why has it become a problem?
Japanese knotweed is not native to Europe, therefore the pests and diseases that control it in Japan are not present in the UK. In Japan, Japanese knotweed grows in harmony with other plants and only grows to a fraction of the size that it does in the UK. Similarly, many British plants that have been taken abroad have become highly invasive elsewhere.
Japanese knotweed is a problem throughout Europe and most of North America. Its vigorous growth excludes almost all of our native species, which cannot compete with the tall summer growth or the thick mulch of decaying canes and leaves in winter. Many of the insects that are dependent on our native plants are also lost.
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© Cornwall Knotweed Forum.
The information on these pages has been compiled by the Cornwall Knotweed Forum from information provided by its members and partners. It is provided in good faith to the raise awareness of the issues and to promote best practice in the control of Japanese knotweed. The information may be used freely for private and educational purposes but may not be copied for commercial use. We update information and advice on a regular basis. However the Cornwall Knotweed Forum, or any of its constituent members cannot be held responsible for the efficacy of the treatments described, or any damage to persons, property or the environment that arises from interpretation of the advice given.
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