Japanese Knotweed

This ornamental garden plant was first brought to England from its native Japan in Victorian times. The plant currently has no natural predators in this country and grows rapidly. For these reasons, once established, it will quickly outgrow all other plants and dominate any garden or vacant plot, rendering the space unusable for amenity purposes. The roots (known as rhizomes) are very strong and can damage structural elements of buildings (such as floors and walls) along with underground services. The plant spreads using its rhizomes, which can travel a horizontal distance of up to seven metres. The plant grows to a vertical height of three metres. It was once confined to land bordering rail lines and rivers, but now can be found almost anywhere. It has distinctive large leaves with a flat base, while the stems/stalks are tightly packed together and have a red colour. The leaves grow in an alternate style on the stem. In late summer, the plant produces small white coloured flowers. If cut, the stem will be found to be hollow. However, under no circumstances, should the plant be cut down as this will only cause it to spread further. In most domestic situations, it will be practical to eradicate the plant using chemicals, which are either injected into the stems or sprayed directly onto the leaves. This treatment will have to be repeated yearly for at least three years. Normally a guarantee is then provided for a term of at least a further five years. Most mortgage lenders will lend on buildings where Japanese Knotweed is growing nearby, subject to an eradication/treatment plan being in place (which will need to be fully paid for in advance). However some lenders are more cautious and will not lend on buildings where the plant is confirmed to be growing within the seven metre spread radius. For this reason, deliberate concealment of Japanese Knotweed infestation is on the increase by people selling their property. Other problems can arise where the plant is growing on the border between two or more properties. Not only can it be difficult to determine on whose land the infestation started, but the organisation of an effective joint treatment/eradication strategy can prove difficult. In the event of a border dispute, the use of a root barrier may be considered, although opinion is divided as to their effectiveness.


← Useful info