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Buying or selling a house with Japanese knotweed

4 min read

Japanese knotweed is an invasive plant that can affect your property and value. Here, we explain how to identify it, and ways to safely remove it.

  • Abigail Bolton Senior Digital Website and Content Marketing Executive
    Abigail Bolton

    Senior Digital Marketing Executive

    Published January 23rd 2024

invasive Japanese knotweed growing in the garden of an picturesque english house

What is Japanese knotweed?

This plant is native to Japan, China, Korea and many other Asian countries.  It was brought to the UK as a decorative garden plant in 1900’s and has since spread rapidly across the country. It is known to spread vigorously once planted and can be found growing near water sources such as lakes and ponds, and also near building and houses and particularly near railway lines across the UK.

How to identify Japanese knotweed?

Japanese knotweed has very distinctive characteristics and you can spot it by looking for the following:

  • They grow with a thick stem which often resembles bamboo (this can vary season to season) and grows in a Zig Zag pattern.

  • They have smooth green coloured leaves with a pointed tip which grows from the stem.

  • Small white/cream flowers will grow in clusters usually in late summer.

These plants are highly aggressive when they grow and usually grow between 7-10cm per day compared to your usual garden plants and weeds. Please be aware that knotweed can sometimes be mistaken for other invasive plants such as the Himalayan knotweed, Russian vine, Himalayan honeysuckle and Houttuynia.

a close up of Japanese knotweed growing in a back garden

How does Japanese knotweed affect your property?

As this plant is known to grow rapidly and thrives in almost any condition is it exposed to, it can grow around and into the foundations of the property which can damage the buildings structure, causing very serious and potentially very expensive damage.

If you spot Japanese knotweed growing in or around your property you should NOT ignore it, it would be wise to take responsible action before the growth damages your property further.

How does it affect the purchase or sale of a property?

Having Japanese knotweed growing in or around your property is a cause for concern for both property buyers and sellers and could impact you in various ways.

  • Majority of mortgage lenders will be very cautious in lending mortgage to a property which is affected by Japanese knotweed.

  • If your property or a neighbouring property is known to be infested with this plant you may notice a decrease in property value unless it has been treated.

  • As a property owner you will have legal liability for the vegetation, it is against the law to allow this plant to spread from one property to another.

It can sometimes be difficult to sell a property to potential buyers if there is Japanese knotweed growing in your property.  You must declare this to the buyer on the TA6 form.

How do I remove Japanese knotweed

This type of weed is seen as a domineering plant with tough stems and roots which make it very difficult and expensive to remove. However the main concern is the spread of this plant while removing it, which is why it is usually better to allow a professional removal company to do this. The downside to this is the cost implications as it can be expensive; you could be looking at costs from a couple of hundred pounds to several thousand pounds (depending on severity and size of area infected).

Always do your research before agreeing to anything and be aware that any buyer (and their mortgage lender) will expect to see a professional insurance backed management plan in place to ensure the complete eradication of the weed.

If you are looking to remove it yourself, you will need to be swift with the process as it is always best to remove the weed as soon as possible. There are several ways in which you can explore removing the weed yourself; this is through herbicide treatment, removal /excavation of the infected areas via tools and machinery or stem injection to kill off the weed. Once this plant has been removed ensure that it has been disposed of correctly and that fragments of the roots are no longer present in the soil.

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