Japanese knotweed: what you need to know

by Housesimple on 25th February 2019

While a few tufts of grass and rogue dandelions dotted about the garden aren’t going to affect your home sale, these really aren’t the weeds you should be worried about. Japanese knotweed, on the other hand, brings with it a whole array of issues that you’ll need to address right away before they get out of hand.

This large perennial plant not only has the power to affect your home valuation but it also puts off around 78% of buyers according to new YouGov research.

Although 76% of British adults have heard of the plant only 19% of Brits claimed that they could correctly identify the plant and there are still plenty of homeowners who don’t know about the structural damage it can cause and the legal issues that come with it.

However, there’s no need to panic – before you put your home on the market, it’s time to hear the facts about this leafy home invader and how best to nip it in the bud.

What is it?

Japanese knotweed is a bamboo-like plant with white flowers that was first brought to the UK from Japan in the 1850s. It was originally grown here as an ornamental plant, although many farmers used it to feed cattle and other livestock.

In Japan, the plant is kept under control thanks to indigenous insects, but there's nothing to restrict its growth here in the UK. It can increase in size quite quickly, sometimes over a yard a week. In warm, sunny weather it can even grow by 10cm per day.

Why does it cause problems?

Buildings are no match for Japanese knotweed. This plant can grow up to three metres high and spreads rapidly, pushing through concrete, asphalt, drains and even into your property’s cavity walls in search of light and water.

This leafy pest is now considered the most invasive plant species in the UK by the Environment Agency and has made it into the top 100 of the world’s worst destructive plants.

Every year, the British Government spends around £166 million treating affected areas, and it’s estimated that it would take £1.5 billion to completely eradicate the species from the county.

What does it matter to me?

In 1981, the Wildlife and Country Act made it illegal to introduce Japanese knotweed into wild spaces. Not only that but, if you don't treat the spread of this plant on your own property, you could be served with an Antisocial Behaviour Order that could lead to a fine or even a jail sentence – especially if it spreads to your neighbours’ properties.

Out of those homeowners who’ve heard of the plant, only 36% know that they’re legally responsible for preventing it from spreading and therefor could be sued, and a mere one in five realise they could end up with an ASBO.

What’s more, plenty of lenders have refused mortgages on homes with knotweed infestations.

If Japanese knotweed shows up on a homeowners survey the seller will usually have to foot the bill for a specialist report to be commissioned. The report will assess the risk level on the RICS scale and detail how the knotweed can be treated. The two parties will then decide whether or not to go through with the sale and how to go about removing the plant from the property.

How do I get rid of it?

If you find Japanese knotweed in your home you should never attempt to remove it yourself but instead hire a professional. The plant can now be extracted from a property in only a few days using a digging out method, which means sifting the earth to take out all the roots from the infected soil.

Once all traces of this invasive species have been dealt with, it’s a wise idea to take out an insurance-backed guarantee for as little as £67 to prevent any further mortgage issues arising in the future.

With this quick-growing species, it’s all about dealing with it quickly, calmly and by the book.


Photo credit Environet UK

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