Japanese Knotweed

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What is Japanese Knotweed?

Japanese Knotweed (Fallopia japonica) is one of a number of invasive species covered by the Wildlife and Natural Environment Act (NI) 2011. Originally introduced as an attractive plant from Eastern Asia, it was introduced to Europe many years ago, since when it has proliferated. As in the rest of the Europe, in Northern Ireland and the Republic of Ireland it has become a major problem, largely because of its ability to infiltrate concrete and brick, leading to a weakening of building foundations.

Bad News

Japanese Knotweed can:


Reduce the value of your home

(see Daily Mail article from September 2014)



Damage the structure of your building


Take years to eradicate


Get you a criminal record

(see Daily Telegraph article from October 2014)


Selling your property

Knotweed can prevent a purchaser getting a mortgage on your house and can cause legal problems if it spreads to neighbouring properties.

Good News

With the correct treatment, Japanese Knotweed can be eradicated.


Treatment will help lenders consider a mortgage on the property.

Once treatment starts, most lenders will accept our indemnity and consider a mortgage on the property.


We can stop the damage immediately

The damage to your property will stop as soon as treatment starts.


Treat & Manage your infestation

Our team will discreetly treat and manage your infestation, and provide you with the reassurance of our indemnity insurance


We can manage your infestation

Our expert horticulturists will provide advice on the best way to manage your infestation.

Identifying Japanese Knotweed

Japanese Knotweed has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not closely related. While stems may reach a maximum height of 3-4 m each growing season, it is typical to see much smaller plants in places where they sprout through cracks in hard surfaces or are repeatedly cut down.

The leaves are broad oval with a truncated base, 7-14 cm long and 5-12 cm broad, with a smooth edge.

The flowers are small, cream or white, produced in rows along a branch, and appear in late summer and early autumn.

Appearing in Spring, new shoots resemble asparagus spears.
The leaves are palm-sized broad ovals with pointed tips.
Late summer
The small white flower appears as attractive fronds.
The leaves fall away leaving bamboo-like hollow stems.

How can I get rid of it?

Chemical treatment

The simplest and most cost-effective way to get rid of Japanese Knotweed is by chemical injection into the stem - although it can require several years’ treatment to ensure complete eradication. This is a specialist task and should not be attempted by non-specialists. Although it can take several years for the complete removal of the Japanese Knotweed, the good news is that as soon as treatment is started damage to your property will be stopped. We carry indemnity cover, and this will be accepted by most mortgage lenders.



In some situations, such as construction sites, a more immediate solution is required. In these cases it is necessary to remove contaminated soil from the affected site. As growth occurs from the plant’s roots, the worst thing that can be done is to disturb the soil before treatment, as this can spread the invasion over a much wider area.

To ensure complete removal, it is necessary to ensure all roots have been removed, and in undisturbed soil this involves digging to a depth of three metres. There are two ways in which soil can be removed.

Dig & bund

Infected soil is moved to a ‘quarantine’ area on-site and then given chemical treatment. After treatment is completed and the site is certified as clear, the bund can be built on - or landscaped.

Dig & remove

Infected soil is removed from the site completely and disposed of in licensed landfill sites. Knotweed NI has negotiated suitable landfill sites for a number of clients, and is well placed to help carry out this process as speedily as possible.


Root Barrier Installation

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If you have any questions about Japanese Knotweed or any other invasive species, please get in touch.