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What is Japanese Knotweed?

Napthens - April 27th 2017

Japanese Knotweed arrived in Britain in 1850 as an ornamental plant, labelled “Plant number 34” in a box of 40 Chinese and Japanese varieties that were delivered to Kew Gardens. It is a strong-growing perennial.

Why the concern?

Japanese Knotweed can have a devastating effect on property values.  The plant can grow extremely quickly and during the summer months it can grow at a rate of 10cm – 20cm per day.  The plant can cause structural damage to properties as it can push up through the foundations and drains.  As a result, few mortgage lenders will offer loans where the plant is found growing within 7 metres of the property.  It is no surprise that this has the effect of substantially reducing the value of affected properties.

The only way to destroy Knotweed is by treating it with chemicals, usually over a 5 year period.

Do sellers need to disclose the presence of Japanese Knotweed to potential buyers?

Sellers are under a legal duty to disclose Japanese Knotweed in the Property Information Form. The form specifically asks sellers whether the property is effected by Japanese Knotweed.  If the property is effected then the seller is asked whether there is a management plan in place.

If your clients’ property is effected by Japanese Knotweed, they will need to be upfront about the fact and to reassure a potential buyer and their mortgage lender, it is advisable to seek help from professionals and put a treatment plan in place.  The British Association of Landscape Industries (BALI) has a directory of members offering invasive weed control.

Legal enforcement

It is not illegal to have Japanese Knotweed in your garden.  However, homeowners should aim to control Japanese Knotweed to prevent it from causing a problem in the neighbourhood.

If problems do occur in neighbouring gardens, then homeowners should speak to/correspond with their neighbours before contacting their local council to talk about enforcement.

It is an offence under Section 14(2) of the Wildlife and Countryside Act 1981 to “plant or otherwise cause to grow in the wild” any plant listed in Schedule Nine, Part II to the Act, which includes Japanese Knotweed.  All parts of the plant and any soil contaminated with the rhizome, are classified as “controlled waste” requiring all the “duty of care” requirements under the Environmental Protection Act 1990 to be met. Therefore, individuals could be fined up to £5,000 or sent to prison for up to 2 years if they allow contaminated soil or plant materials from any waste they transfer to spread into the wild.

Interesting facts about Japanese Knotweed:

  • Japanese Knotweed has been found to be edible between mid April to May just before the stems become hard and woody. They can be steamed and eaten like asparagus!
  • As well as being a good source of vitamin C, it’s said to taste like rhubarb with a hint of lemon.
  • Japanese Knotweed can lie dormant underground for a decade, and it can take up to 5 years for poison to kill it completely

For more information on this topic or for any other queries, please contact one of the Residential Property team.