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Japanese Knotweed – Untangling the truth about this troublesome triffid

Most people have probably heard horror stories in the press about the scourge of Japanese Knotweed and the effect it can have on a property, its value and the chances of being able to sell a property that is infected by it.

If you suspect that you may have Knotweed on your property then you should gain professional advice on its treatment and eradication. This article is not intended to be a definitive document and is not a substitute for professional advice, but it may help you identify the plant and help to point you in the right direction for getting help and proper advice.

What is Japanese Knotweed?

It’s an ornamental shrub that was introduced in the 19th century to the United Kingdom. It is characterised by its bamboo-like appearance with a central cane like structure which is hollow and has characteristic patterns of purple speckles. In the winter time the stems turn brown and die back to ground level. Come spring, it will produce red tinged shoots until it flowers in late August to early September.  The flower is small and white.

Why is it such a problem?

Japanese Knotweed can grow extremely quickly at rates of up to 2cm per day.  It is a non-native plant and appears to have no natural enemies in the UK to keep it in check.

Knotweed can grow from extremely small sections of its root known as rhizomes and these can grow through tarmac and the foundations of buildings to reach the full height of approx. 3 metres.

The Legal Considerations

Whilst it is not illegal to have Knotweed growing on your land, you must not knowingly plant or cultivate it. You do have a responsibility to ensure that the plant does not spread onto neighbouring land.

You must ensure that any cuttings or contaminated soil are properly removed from your property by an authorised specialist contractor.

You could be fined up to £5,000 or face up to 2 years in prison if you allow contaminated soil or plant material to spread into the wild.

How do I treat it?

Its probably best to get a suitably qualified and authorised contractor to deal with the treatment of any outbreak. The plant can be treated with chemicals, but this can take up to 3 years to kill off the root systems properly.

If you do have an outbreak it is best to get it treated professionally as soon as possible, especially if you are thinking of selling the property in the near future. It is very unwise to try and treat it yourself as it is likely to be picked up by the surveyor who surveys the property for your buyer, if there is no treatment plan in place then it is likely that your buyer will be asking some very tough questions. The Royal Institution of Chartered Surveyors has published 5 levels of severity ranging from level 1 where no knotweed is present at the property, or any surrounding properties,  to level 5 where knotweed has been spotted within 7 metres of a habitable building, or is evident within the boundaries of the subject property, or a neighbouring property and/or has caused damage to paths or the structure of the subject property damage.

As always proper professional advise is crucial in order to remove the outbreak properly, backed with a suitable waste removal certificate and a guarantee.