An Introduction to Japanese Knotweed
Japanese Knotweed (scientific name: Fallopia japonica) is a tall, vigorous, hardy perennial plant. It is an invasive, non-native plant pest and is considered one of the most problematic plant species in the Britain.
In 1825, it was introduced to the UK as an ornamental plant for large gardens, prized due to its imposing size and sprays of creamy white flowers. By 1886 it was established in the wild and now it is very widely distributed.
Owing to its non-native origins, Japanese Knotweed found in the UK has never been exposed to any of its natural enemies, such as the insects, bacteria and fungi that feed and grow on and in it, and naturally check its growth, as occurs in places like Japan, Korea and North Western China. The absence of these natural measures to balance the ecology, allied to its extremely invasive and competitive nature, has been the driving forces the invasive spread of Japanese Knotweed throughout the British Isles
Explanation of Legislation and Responsibilities
It is not against the law for landowners to have Japanese Knotweed on their property. However, if it can be shown that the plant has spread from their property onto another property, then they could be considered responsible for any damage caused and the costs of control, these costs can be significant.
If landowners take all reasonable steps, and exercise all due diligence to avoid spreading the plant, then they will be better protected against prosecution. In order to reduce the potential of fines/prosecution, landowners should have a management plan for the Japanese Knotweed on their property and be able to show that they are following it, e.g. they have hired a specialist in the control, management and eradication of Japanese Knotweed and are following the advice and measures given
In England, Wales Scotland and Northern Ireland Japanese Knotweed and soil containing Japanese Knotweed can only be disposed of at waste facilities authorised to receive controlled waste specified to be Japanese Knotweed.
Japanese Knotweed is coverd by The Wildlife & Countryside Act 1981 and The Environmental Protection Act 1990.
Identifying Japanese Knotweed
The stems are sturdy and zigzagged, with purple spots and are hollow, being similar to Bamboo. The flowers, which blossom late summer /early autumn, are cream/off white in colour and are formed in drooping clusters, usually between 3 and 5 inches long.
In spring, the emerging stems are green to red/purple with rolled leaves that unfurl as the shoots extend. At the end of the year, the stems persist and turn various shades of brown, sometimes with an orange tinge.
Externally, the rhizome appears dark brown and has a resemblance to leather. When the growth is fresh it is brittle and will snaps with little effort. The internal appearance is orange/yellow in tone, with the darkest of the colours most often found in its centre. Lines often radiate outward from the middle.
Shoots and rhizomes emerge from an enlarged crown which develops at the base of Knotweed stems. This crown is firm and uneven in appearance and prior to the growth season it can possess smooth pink/red buds.