Originating in Japan, in the 1840s a Dutch doctor called Phillipe von Siebold brought the Japanese knotweed over to Britain. He began selling the plant to botanical gardens and high society figures. By 1869, it became available for public sale, and farmers started using it as feed for their animals.

In the late 19th century, Japanese knotweed was unleashed on our gardens. Encouraged to buy at the time, it was described as “a capital plant for small-town gardeners.” However, perceptions soon changed.

In 1981, the Wildlife and Country Act made it an offence to introduce Japanese Knotweed into wild spaces, and a survey in 1998 showed that in the Swansea area alone, the weed-covered an area of 99 hectares. In 2011, aphids were released in Swansea to try and combat the crazed plant, without much luck.

How Did It Spread in Britain?

This aggressive knotweed has plagued British countryside, striking fear into homeowners and causing devastating impacts on a property. But what makes Japanese Knotweed so unusual from other garden weeds?

This knotweed takes first place as the UK’s most invasive and destructive plant. Known to have ravaged through tarmacked drives and trespass homes, it can creep underneath houses, as well as garden buildings such as sheds and greenhouses, and reach up through your floorboards.

In an attempt to control its growth, it costs the government thousands of pounds every year.

Although it produces seeds, it’s extremely rare for the seeds to germinate. The most common method of dispersal is the spreading of rhizome fragments (shoot-like-roots).

The crown can survive drying or composting and will produce new canes when it comes into contact with soil or water.

To dispose of knotweed canes, it is crucial the stems are cut above the crown, rather than pulling as this will dislodge the crown. Living crowns usually have growth buds which are obvious in late spring and which have a characteristic pink colour.

Did You Know You Could Be Breaking the Law?

In the UK, there are two main pieces of legislation surrounding Japanese Knotweed.  

The Wildlife and Countryside Act 1981 states that it is an offence to plant or let Japanese Knotweed growing in the wild. 

Section 14(2) of the Wildlife and Countryside Act 1981 also states, “If any person plants or otherwise cause to grow in the wild any plant which is included in Part 2 of Schedule 9, he shall be guilty of an offence”. (Japanese knotweed is a Schedule 9 listed plant).

An offence under the Wildlife and Countryside Act can result in criminal prosecution.

Environmental Protection Act 1990 classifies the weed as ‘controlled waste.’ This means by law; you must dispose of it safely at a licensed landfill site.

Soil containing rhizome, the root-like stems of the plant, is regarded as contaminated. It must be disposed of an official landfill site and buried to a depth of at least 5 metres.

According to the Environmental Protection Act (EPA) 1990, any controlled waste, must be disposed of at appropriately licensed landfills. If you deposit, treat or keep controlled waste without a licence it is an offence under Section 33 of the EPA.

A violation of the Environmental Protection Act can result in an unlimited fine. You can also be held liable for costs incurred from the spread of Knotweed into adjacent properties.

The Control of Pesticides Regulations 1986 requires any person who uses pesticides, “…to take all reasonable precautions to protect the health of human beings, creatures and plants to safeguard the environment and to avoid contaminating the water.”

If you plan on using pesticides near water, seek approval from the Environment Agency first. Allowing it to spread from your land can make you liable to third-party litigation and/or civil prosecution.

Not disposing of Japanese knotweed under the Environmental Agency Regulatory Position Statement ‘Treatment and disposal of invasive non-native plants: RPS 178’ could easily result in spreading the knotweed and therefore breaking the law.

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