What’s knotweed and what’s not knotweed?

Summer’s here, and you know what that means: ice cream vans, six-weeks holidays and the annual invasion of Japanese knotweed.

Simply put, Japanese knotweed is Britain’s most invasive non-native plant. It was originally brought back to Britain in the middle of the 19th Century by the Victorians to be used as ornamental plants that could be used to liven up residential gardens. In more recent memory, it is alleged that it was used to stabilise loose soil in Welsh coal mining valleys and hide and stabilise railway embankments.

The plant evolved to survive in its native Japanese volcanic landscapes where regular ash deposits meant that it was only able to survive thanks to its deep root system. Due to not having anything this crazy in Britain and with nothing to fight against, the plant is able to prosper unabated with its roots being able to tunnel 3m deep and 7m wide, wrecking property foundations, drainage systems and sewers in its path.

Japanese knotweed
Japanese knotweed It can often be confused for honeysuckle, chameleon plants or Russian vine, but you can recognise Japanese knotweed by its little spade-shaped leaves and cream-coloured flower. Don’t be fooled by its flowers though; it is a civil offence to let it grow and you could be fined for damages. If you are selling your house or land that is currently being ravaged by Japanese knotweed, you must state it in a TA6 form available from your conveyancers. It is vital that this is done to avoid disputes with your buyers later in the process.

So, once you’ve stopped panicking and reminded yourself that it isn’t poisonous or dangerous to you or others, what do you do if you find Japanese knotweed in your garden?

Several organisations have provided advice including the Royal Institution of Chartered Surveyors, the Environment Agency and the Property Care Association. The RICS Japanese knotweed information paper suggests there are 4 different removal and treatment methods.

1. Excavation of the plant and its roots and soil – these are removed to an off-site, licensed waste management facility.
2. On-site burial and or encapsulation with membranes – covered with 5m or more of overburden or the use of a specialist membrane. The use of an on-site barrier is a popular technique if knotweed encroaches from a neighbour’s land.
3. Biological control – involves introducing a pest species that will attack and control the Japanese knotweed.
4. Chemical control – involves the use of special herbicides over several growing seasons. This is usually the cheapest method but can take several years to become effective.

Japanese knotweed is prevalent throughout the UK and coastal areas of Ireland – it’s way more common than you think, so make sure you aren’t hoarding some in your garden today.

If you have an issue or a query about knotweed, please ring 0800 021 6789 to speak with one of our surveyors.

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