Is Japanese Knotweed Dangerous?


You’ve probably heard by now some of the horror stories of Japanese knotweed, (Fallopia japonica).

Structural damage, decimated property values and mortgage providers refusing to lend. These are all possible consequences of an untreated knotweed infestation.

Maybe you’ve heard about how the ongoing invasion of Japanese knotweed damages biodiversity by supressing native species.

Perhaps you’ve read about people being injured by other invasive species like giant hogweed (Heracleum mantegazzianum).

Nobody wants to see knotweed on their property for a number of very good reasons, but is Japanese knotweed dangerous? Could contact with it harm people or pets?

Well, the good news is that Japanese knotweed is non-toxic and perfectly safe to handle. Despite its fearsome reputation, it is completely harmless to humans and animals.

In fact, Japanese knotweed is edible! The young shoots can be eaten raw or made into pies, crumbles, pickles and chutneys, or any recipe which calls for rhubarb. The older stems which are too tough to eat can be made into syrup for flavouring soft drinks or cocktails. Flower buds can be used for fermentation, to make wine and beer.

Japanese knotweed has been used for centuries in traditional medicine. Known in China as Hu Zhang, the dried root is used to treat many ailments including jaundice, coughs, congestion, inflammation and snake bites. It is also gaining popularity in the world of alternative therapy, as it contains an anti-oxidant called resveratrol.

While the claims of snake oil manufacturers should be treated with caution, resveratrol is also of interest to the scientific community as an anti-inflammatory, cardioprotective and anti-carcinogen. Clinical trials are yet to be completed, however.

You can visit the Japanese Knotweed Agency Gallery here and see what Japanese Knotweed looks like through the 4 seasons to help you easily identify the dreaded weed at the earliest opportunity. And there’s a whole load of real-life photos taken by the Agency Surveyors across the UK, to give you a feel of how rampant this weed is and how it can literally grow anywhere.

If you are unsure whether the suspect plant or weed is indeed Japanese Knotweed of a kind, you can submit a photograph to us here at the Japanese Knotweed Agency and one of our surveyors will assess and confirm whether it is or isn’t Knotweed, typically within just a few hours. Use our free identification service here.

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Capital Punishment for Japanese Knotweed

Electro-Thermal Treatment for Japanese Knotweed


Manchester based Japanese Knotweed Agency launched in 2018 to support businesses, Local Authorities and Housing Associations, but ultimately to support Home Owners who are affected by Japanese Knotweed to understand the legal and financial implications of having a Japanese Knotweed issue.

The surprising fact is that very few have heard of Japanese Knotweed, and even fewer are aware that it is present in their garden or on their land as they could not identify the UK’s No.1 Invasive Weed, even though in 2022 we seen a massive rise in infestations growing well over 10 and 12 feet tall.

Herbicidal treatments still do have a lot of use in trying to bring this invasive weed under control, but what are the problems and longer-term effects of using chemicals to treat Japanese Knotweed, and how do they compare to the new Electro-Thermal treatment now available in the UK?


Killing Japanese knotweed

When it comes to ‘killing’ Japanese knotweed, treatment and eradication can be a tough task and take several years to get the weed under control and eradicate – but it is possible with commitment.

Herbicide spraying was the only available treatment for killing Japanese knotweed. However, it’s important to know that herbicide will kill most of the plant, but it doesn’t totally eradicate the plant’s rhizomes (extensive root system) in the ground. This means that future re-growth is technically possible if not managed.

Continued multiple yearly applications of herbicide can prevent the spread and growth of Japanese knotweed, but if you want the knotweed’s rhizomes (roots) completely removed from the soil – excavation was required. This was the way to ensure complete Japanese knotweed removal.


Herbicides that Kill Japanese Knotweed


Does Roundup kill Japanese knotweed?

Roundup, Gallup, Landmaster, Pondmaster, Ranger, Rodeo, and Touchdown are all herbicides recommended to kill Japanese Knotweed. They are all glyphosate-based herbicides and will somewhat prove effective in treating the troublesome knotweed, safe to say what the eyes can see!

The best time to spray the leaves of Japanese Knotweed with herbicide is late summer or early autumn. This is the period in which the plant is flowering and so the foliage conducts more nutrients to the rhizome to build food reserves.

About glyphosate-based herbicides

Glyphosate-based herbicides will kill Japanese knotweed, but be careful, since these are non-selective herbicides, they will kill whatever plants they come into contact with, whether that’s Japanese knotweed or your prize geraniums. For this reason, many gardeners don’t like using herbicides, but in the case of Japanese knotweed, it is one of the few really efficacious solutions.

Glyphosate is a translocated herbicide as opposed to a contact herbicide. While contact herbicides may appear to be effective against Japanese knotweed, they are in fact only killing its leaves and shoots. This is why it is best to use a glyphosate. As a translocated herbicide, glyphosate is taken partially down into the plant’s roots where it does affect the root system to some extent.


How long do glyphosate herbicides take to work?

Glyphosate-based weed killers available from garden centres will all have a harmful effect on Japanese knotweed. This is normally a slow process requiring at least three to four growing seasons to be effective, and hinder the growth of Japanese knotweed. Professional Japanese knotweed removal companies have access to more powerful herbicides which can reduce the removal process typically by half.

Are there any other chemicals that kill Japanese knotweed?

Japanese knotweed is also susceptible to other chemicals like triclopyr and picloram. However, glyphosate is often the preferred choice for domestic use due to its suitability for use near water.

A word of warning with herbicides

While herbicides are an effective means of killing Japanese knotweed, their use should be limited to areas destined to become lawns or flower beds, do not use herbicides on areas that will one day become your vegetable garden.


You should also be extremely careful of areas that have had herbicidal treatment and as a big safety rule, do not let children or animals anywhere near the treated area.

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Varieties of Knotweed in the UK


You may well be aware of the infamous Japanese Knotweed (reynoutria japonica or fallopian japonica) which has been causing headaches for homeowners up and down the U.K. If not, you should visit the Japanese Knotweed Agency Gallery here and see what Japanese Knotweed looks like through the 4 seasons to help you easily identify the dreaded weed at the earliest opportunity. And there’s a whole load of real-life photos taken by the Agency Surveyors across the UK, to give you a feel of how rampant this weed is and how it can literally grow anywhere.

Japanese Knotweed is believed to account for 98% of the Knotweed in the U.K. There are, however several other varieties at large in the British Isles.


Lesser Knotweed:

Known, confusingly, by several different names (Persicaria campanulata, Polygonum campanulatum, Polygonum campanulata, Reynoutria campanulatum), lesser Knotweed is not as invasive as other varieties, but is still a vigorous plant. Rarer in the U.K. than other species, it is more likely to be found in Scotland and Northern Ireland.

Plants grow to a height of 2-3ft (60-90cm). The stems do not exhibit the familiar “zig-zag” pattern of its cousins.

Leaves are elongated, rather than heart-shaped, and vary considerably in size, displaying a “herringbone” pattern of grooves and sometimes reddish veins. The underside is paler, with fine white hairs.

Around mid-summer, tiny white or pale pink, bell shaped flowers appear in loose clusters.


Dwarf Japanese Knotweed:

Dwarf Japanese Knotweed, (Reynoutria japonica Houtt, Polygonum pictum, Polygonum compactum, or Polygonum reynoutria), as the name suggests, is a smaller form of Japanese Knotweed, rarely growing to more than 3ft (1m). Although less invasive than standard Japanese Knotweed, this dwarf variety is present as both male and female plants so may set viable seed and lead to further hybridisation.

Usually appearing in late spring, its leaves are darker and more variable in form than japonica. Lacking the distinctive “heart” shape, they are more oval, with wavey edges and a leathery texture.

Stems display the distinctive “zig-zag” pattern and reddish colouration of its larger relative.

White or pale pink flowers appear in late summer, forming upright spikes which can darken towards red as they mature.


Himalayan Knotweed:

One of Britain’s rarer Knotweeds, Himalayan Knotweed, (Persicaria wallichii, also known as Aconogonum polystachyum, Reynoutria polystachia, Persicaria polystachya, Polygonum wallichii, or Polygonum polystachium) is most likely to be found in southwestern England. Although sometimes mistaken for lesser Knotweed, Himalayan Knotweed is much taller, rapidly growing to 6ft (1.8m). It is a hermaphrodite and can self-fertilise, leading to greater invasive potential.

Leaves are darker and more elongated than those of Japanese Knotweed, typically 4-8in(10-20cm) in length and tapering to a sharp point. Leaf shapes vary, some tapering to the base and others forming a more heart-shaped lobe.

The zig-zagging stems are hairy, and although some stems show a familiar pinkness, they are more likely to be green. A distinctive feature is the brown sheaf which is retained at the base of the leaf stem.

Himalayan Knotweed flowers between mid-summer and late autumn, producing white or pale pink blossom in open clusters around 8-14in (20-35cm) in length.


Giant Knotweed:

Closely related to Japanese Knotweed and broadly similar in appearance, Giant Knotweed (Reynoutria sachalinensis), is, as one might surmise, a much larger variety than its more common relative, growing 13-16ft (4-5m) high. It has a shorter growing season than japonica, appearing later in the spring and dropping its leaves earlier in the autumn. Male and female plant are present in the U.K. and Europe, meaning that this variety can spread by seed dispersal as well as via the rhizome.

Leaves are much larger than japonica, reaching 16in (40cm) long and 11in (27cm) wide, but retain an elongated “heart-shaped” form. They are wrinkled around the edges and have white hairs on the underside.

Dense clusters of creamy flowers appear in late summer and early autumn.


Bohemian Knotweed:

Bohemian Knotweed, (Reynoutria x Bohemica) is a hybrid of Japanese Knotweed and giant Knotweed which has only been classified as a separate species in recent decades. Bohemica grows to an average 8-10ft (2.5-3m), but sometimes reaches 13ft (4m). Both male and female plants have been seen in Britain and Europe. This means that bohemica can fertilise and set seed, potentially making it more invasive than the infamous japonica.

Leaves are larger than Japanese Knotweed, reaching 10in (25cm) long and 7in (18cm) wide. They retain the familiar heart shape, but are a darker shade of green and more crinkled in appearance.

Flowers appear in late summer and early autumn, and are pale green or creamy white.

If you are unsure whether the suspect plant or weed is indeed Japanese Knotweed of a kind, you can submit a photograph to us here at the Japanese Knotweed Agency and one of our surveyors will assess and confirm whether it is or isn’t Knotweed, typically within just a few hours. Use our free identification service here.

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Pinkweed – a new type of Knotweed


Many people have been contacting us regarding a pink form of knotweed which has been causing some confusion amongst gardeners and property owners.

There are several species of knotweed which take distinct forms and appear in many sizes. Some are relatively harmless, but the pink variety is considered an invasive species by the U.K. government.

Pink knotweed proliferates rapidly, creating a thick carpet of vegetation which supresses the growth of other plants.

Although pink knotweed evolved in harsh, high-altitude environments, it is extremely adaptable and is happy growing in both boggy, wet ground and drier, sandy soils. Depending on local conditions, it can be either annual or perennial, and even evergreen in warmer climes.



It is distinct from Japanese knotweed in several ways:

Usually grows to only 6in (15cm) high

Spreads horizontally to about 5ft (1.5m)

Prefers wet ground, but will grow almost anywhere

Forms a dense ground cover

Smells of urine

Leaves are elongated and range from 2in in an annual to 11in in a perennial specimen. The edges are a dark red, as are the stems and the “v” shaped marking on the leaf surface.

Small, pink globular flowers, which protrude above the foliage.

If you are unsure whether the suspect plant or weed is indeed Japanese Knotweed of a kind, you can submit a photograph to us here at the Japanese Knotweed Agency and one of our surveyors will assess and confirm whether it is or isn’t Knotweed, typically within just a few hours. Use our free identification service here.



Pink knotweed can reproduce both vegetatively and sexually, depending on local conditions. Like the better-known Japanese knotweed, it spreads by extending new shoots from a large, underground rhizome. Unlike its Japanese cousin, it can also reproduce by setting seed.

It’s vigour and adaptability mean that it can be difficult to control or eradicate. Any small piece of the rhizome which is left in the soil can lie dormant for years before growing into a new plant.


There are three options for getting rid of a knotweed infestation:


Chemical spraying will kill off the above-ground growth and slow the spread.


Digging out and removing contaminated soil should be undertaken by specialists, as small pieces of root can grow into whole new plants, and transport and disposal of the waste requires specialised licences.

Electro-thermal treatment:

A powerful electric current is sent through the plant, from the stem, through the roots and into the soil. This causes the water in the plant to vaporise, disrupting the plant’s tissues, and effectively removing any moisture the weed would use to grow rendering it in a dried/dead state. Unlike herbicidal treatments, this new electrical method gives immediate results and uses no harmful chemicals. The electro-thermal treatment because it uses up to 5000V spreads from the stem right across the vast underground root system and is ultimately the most effective treatment available in the UK. Whilst this treatment is fairly new in the UK, Prince Charles is said to own one and uses it on the Royal estates, and Transport For London (TFL) have used the machines with massive results throughout 2022.

Japanese Knotweed Agency are so impressed with the technology and results that we will start to offer this effective treatment in early 2023 direct to homeowners who are affected by Japanese Knotweed.


If you have any questions or concerns, please contact:

  • Japanese Knotweed Agency, Hexagon Tower, Crumpsall Vale, Manchester M9 8GQ
  • Freephone: 03335 777 888
  • Monday / Friday: 9:00AM to 5:00PM
    Saturday / Sunday: 9:00AM to 5:00PM – by email or voicemail
    Public Holidays: Closed (Email only)
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The worst exposed Japanese knotweed hotspots in the UK

Is the invasive species in your back garden? Japanese Knotweed Agency map the areas in the UK most at risk from Japanese knotweed

Japanese knotweed is a lot more common in the UK than you might think – and it costs the UK economy over £40million a year.

The plant, native to Asia, was initially brought to the UK in 1850 in a box delivered to Kew Gardens and was much sought-after for its pretty flowers. However, its fast-growing roots led to a wild proliferation – and now the plant can be found all over the UK.

Bolton has been revealed as the Japanese Knotweed capital of the UK in 2022, with the North-West of England making up three of the top four most badly affected locations.

Bristol comes in second and St Helens in third, while Wales is another particularly hard-hit region, with three places in the top 10.

So, what are key attributes of Japanese Knotweed and where are the most badly affected areas in the UK?

Japanese knotweed can grow several inches a day

It hibernates through winter and reawakens in the spring and spreads rapidly, with its root network expanding at an alarming rate. By midsummer, it can grow by several inches a day, and can be identified by its creamy white flowers which bloom around August.

Each root can grow to be three metres deep and several metres horizontally, often piercing through foundations, driveways and walls and causing extensive damage.

In 2021, Dr Ross Cuthbert, of Queen’s University Belfast, led a project to analyse the economic impact of all the UK’s invasive species, and found that since 1975, the plant has cost the UK economy at least £41million a year.
The majority of [Japanese knotweed’s] economic impact is in house devaluation from when you have knotweed on the property, and also the cost of removing an infestation,

Japanese Knotweed Agency have released their National Register in 2021 and seen over 35,000 records submitted by surveyors, homeowners, members of the public and people who enjoy the countryside. That shows how many infestations have been registered in particular areas which you can search by the first part of your postcode to see what has been reported near you.

Bolton has 684 infestations within a 2.5-mile radius of the town centre, whereas Bristol has 475 and St Helens 441.

Streatham, in south-west London, is the only location in the top 10 in the London area, and came in at ninth with 300 logged infestations.

Rapid urbanisation and a defeatist attitude to the species were to blame for its increased prevalence in the North-West and Wales.
The plant had become such a scourge in these areas that many believed it was too prevalent to begin to combat.

Urbanisation helps spread Japanese knotweed

Increases in urbanisation have also seen more soil being moved from one site to another, taking the plant — which can regrow from a lone, finger-sized piece of root — to new areas which it then takes over.

I think the reason why we see it far more in cities is because there has been more and more human movement of soil. A lot of that goes back to the Second World War when there were huge amounts of materials being buried, moved around, bombed etc and obviously there is still a massive amount of the weed in London.

There is also a lot of it in Wales and the reason for this is that for many, many years, the attitude was, ‘well, there’s so much around that there’s nothing we can do about it’.

Also, because land values are quite low in the area there’s no financial incentive to fully excavate it as opposed to just using herbicides to keep it under control.
If there was a million-pound house in London we would likely say that the value of the property justifies getting rid of the infestation properly, which means digging it up. So that might be a ten grand fee for a £1,000,000 house. But if you did the same in, say, Swansea, that house might be worth £100,000 so the treatment starts to look quite expensive.

So, in these sorts of properties, you would just go for a herbicide treatment and control it that way. But controlling is not killing it and it is most certainly not killing it all which is needed to prevent it spreading.”

According to research, approximately one in 20 homes are currently affected by knotweed, either directly or indirectly.

By publishing the 2022 British Japanese knotweed hotspots we hope to raise awareness and encourage people in the area to be vigilant for signs of knotweed as the growing season takes off, so they can act quickly if needed.

Anyone living near or moving to one of these hotspots would be wise to check their garden carefully, enter their postcode into Exposed to find out how many known occurrences are nearby and if in doubt, seek expert help.

Japanese Knotweed Agency offer a free onsite survey that provides a substantial report highlighting where any crowns of the weed are, its age and route of growth etc, and also checks for up to 58 other invasive plant species found in the UK. There’s a full quotation included by one of their registered specialist firms that comes with an Insurance Backed Guarantee, and the Agency can also advise if you are able to make a claim against a third party for the recovery costs of the treatment and Insurance Backed Guarantee, and also claim compensation for devaluation, with a typical claim value well over £10,000

If you are a homeowner and have Japanese Knotweed on your property, get your free Knotweed survey today:


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Dangerous’ garden plants which can decrease property value by up to 15% – how to identify

WITH summer on its way, experts are urging homeowners to look in their gardens to see if they have certain plants which can “damage” property and “devalue” it.

Buying and selling property is often a stressful time, which can be made even more hard when invasive plants are found in the garden. To help homeowners identify plants before purchasing a new home, or to solve current issues, Japanese Knotweed Agency have unveiled the most “common” plants which can devalue property by as much as 15 percent.

Japanese knotweed is an invasive plant which is identified by its creamy white flowers, bamboo-like stems and shaped leaves. It is the most invasive weed in the UK, infamous for its devastating ability to cause costly damage. Its roots can reach down to 10 metres underground, making it extremely difficult to eradicate, and the spread of the weed could damage pipework, pines and weaken building foundations.

Due to this, Knotweed is listed as a defect to the property by RICS Homebuyer Reports, with the potential to reduce the price of property by as much as 15 percent.

Alan Hoey, Managing Director at the Japanese Knotweed Agency said “It is really important to check yourself or get a professional in to check and take immediate and thorough eradication actions before it gets too late if you find you are affected by Japanese Knotweed.

“We highly recommend you seek professional help when removing Knotweed as they re-establish easily from even the smallest remains of the root system.

If your property is affected by Knotweed and you are the owner, Japanese Knotweed Agency offer a free onsite survey and full report, along with a quotation for a herbicide treatment plan and 10-year insurance backed guarantee by a professional and qualified partner firm.

Request your FREE Japanese Knotweed Survey and Report

Similar to Japanese knotweed, giant hogweed is invasive and can spread very fast. It is often spotted in July and can be identified by green stems with purple shoots and white flowers. The expert said: “Widespread really across the UK, especially found around rivers and ponds, its sap is phototoxic and can cause severe skin burns or scars under sunlight.

“Though not causing direct harm to the property, buyers may still refuse to pay a higher price if present because of its high cost of removal, up to £15,000.”

According to the experts, Ivy is also “dangerous to your house”, with a strong wall-climbing ability. It can cause wall cracks, damage the mortar and bring dampness into the home. “Unlike giant hogweed, English ivy could be removed with bare hands by peeling them carefully off the wall. “It is also possible to kill them by cutting their roots and letting them dry out.

“However, not all wall-climbing plants are harmful, such as Boston ivy, so we recommend consulting a professional before mistakenly cutting some beautiful and safe plants from your wall.”

While most trees cause no harm, the experts said large ones such as poplar, willow and oak can be dangerous if grown close to property.

Poplar trees have fast-growing root systems which can spread out to 40 metres and take up 1000 litres of water and nutrients from the soil. “They could live around 50 years and are harder to remove when their roots grow thicker and bigger as time progresses. Their age, soil type, location, depth all matter when deciding whether your tree is a problem. If grown too close to your property, they could lead to further risks or cracks in foundations, subsidence and other structural defects, potentially costing you £5,000 to £25,000 to repair.”

Another invasive plant which can spread seeds metres away is the Himalayan balsam.

It was brought to the UK in 1839. It grows up to two to three metres tall and has pink flowers in summer and early autumn. It can kill off other plants and reduce biodiversity by stealing lights, nutrients and water.

It does not have physical danger to humans but its significant ecological impact on nature and associated laws are not favoured by buyers.

So, it is recommended to keep this plant controlled or eradicated, and make sure it does not spread to your neighbours’ home as it can be illegal.

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Free Japanese Knotweed Survey – discover the facts about your knotweed

Mrs Walsh wrote: The Japanese Knotweed that grew in my garden was quite large, and the roots were so big and thick I couldn’t cut them with any normal tools. This plant has taken over my garden and I am worried it will damage my foundation if I don’t get rid of it soon. Luckily, there are professionals out there who know how to treat it safely and effectively – but they come at a price! I didn’t want to spend money on expensive treatment though, so I took advantage of the Free Japanese Knotweed Survey available across England & Wales.

What is Japanese Knotweed?

Japanese Knotweed is a non-native invasive weed that was brought into the UK in the 1900’s and today is estimated to affect 950,000 residential properties around the UK. It can cause devaluation of your property, be expensive to treat and/or remove, and can cause untold damage to foundations of your property, affect water and sewerage pipes, and stop you re-mortgaging your property or selling it.

What problems can it cause?

Japanese knotweed is a species of plant that can cause huge problems to buildings, roads and other structures. In fact, if left unchecked, it can cause serious structural damage. Luckily Japanese knotweed is easy to treat and we have a 10-year insurance backed guarantee. If you find it in your garden or anywhere else on your property, call us immediately for a free survey.

How do I treat it?

Only an expert should treat the Knotweed which typically is a 3-year treatment plan within a 10-year Insurance Backed Guarantee

How much does it cost to treat it?

Costs vary depending on the site, amount of Knotweed present, age, type of Knotweed and many other factors. Our FREE and WITHOUT OBLIGATION Knotweed Survey gives you all the facts with an inclusive quotation for treatment and an Insurance Backed Guarantee.

Why are we offering this survey?

Japanese Knotweed Agency operate the UK’s Japanese Knotweed National Register and work with many partners across the UK in the fight to eradicate Knotweed and help people protect their property.

Is there a Guarantee?

If you take up our partners treatment plan after your survey and quotation, once the first treatment has taken place, you are covered by the inclusive 10-year Insurance Backed Guarantee.

How do I take part in the survey?

To request your FREE and WOTHOUT OBLIGATION On-Site Survey, just request a Survey form to your email here:

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Knotweed Survey – Sign up for the free knotweed survey and learn more about this invasive weed.

You have probably seen knotweed in your neighbourhood, and you may have even wondered what it was. Knotweed is an invasive weed that reproduces like crazy and can wreak havoc on your property value, as well as any structures it comes into contact with. Luckily, now you can have a FREE AND WITHOUT ANY OBLIGATION survey about the knotweed on your property and learn more about the invasive species. Click here to sign up for the free knotweed survey today!

What is Japanese Knotweed?

Knotweed is ranked towards the top end of the World’s Most Invasive plant species and should not be underestimated on what adverse effects it can have on your property.

Japanese Knotweed spreads very fast and grows at a rapid pace throughout the summer months in the UK and can exploit all types of land and terrain and even grow through tarmac, brickwork, walls, drains, sewers, cavity walls and literally anywhere it can exploit to will do so.

Knotweed is said to affect 950,000 houses across the UK and can significantly reduce the value of your property, cost thousands of pounds to treat, can stop house sales dead in their tracks, can leave you open to litigation if it spreads from your land on to another person’s land and cost you tens of thousands of pounds.

The good news is that if it is coming from another person’s land such as railway, council land, commercial land and so on, you can typically recover all of the costs of treatment and insurance plus recover a significant cash sum to cover any devaluation of the property value.

How Can I Tell If I Have Knotweed?

You can visit our Seasonal Gallery on the below link and make yourself aware of how Kno0tweed looks throughout the seasons.

How Much Is My Property Worth with And Without Knotweed?

In the very best circumstances devaluation can be 5% of the property price, so £150,000 property value will have a minimum loss of £7,500 – plus the cost of a treatment plan and 10-year Insurance Backed Guarantee.

Where Knotweed is identified to be a fair infestation, and may be evidence of it growing in drains, sewers, close to the property or inside the property, the valuation will decrease significantly. Some severely affected properties have seen a 100% devaluation because of the extreme growth and other factors such as access to be able to treat and so on.

The Knotweed will only get worse, so you need to act fast if you think Japanese knotweed is on your land. In most cases you should be able to recover all costs and get compensation.

How Do I Remove the Weed from My Property?

A specialist treatment firm will typically attend at least once every 3 months and treat the weeds by injecting the stems of every plant again and again, and this will go on for at least 3 years, followed by a 2 year observation by the homeowner.

Once treatment starts, you should then be covered with a 10-year Insurance Backed Guarantee, so if it does come back after the 3-year treatment, your insurance will cover any additional treatments required.

What Should I Do Next?


Your survey will highlight the locations of the crowns of Knotweed and where it is coming from and spreading to; it’s direction of growth and travel, and serious issues, age, and lots more, to give you 100% expert, factual information inside an extensive written report bespoke for your property, and will include a full quote for treatment and an Insurance Backed Guarantee.

How do I get a FREE Survey?

It’s simple and straight forward, just click the link below, enter your details and then check your email for the enhanced form.

We check the completed form first to ensure it is Knotweed that is present so we don’t waste your time or ours. Once we identify the Knotweed, we will arrange a surveyor to attend, and you’ll then get a full copy of the report and then decide how best to proceed.

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Japanese Knotweed and its impact on property values

We all know that Japanese knotweed can be pretty destructive, especially if it’s allowed to grow out of control and invade the landscaping of neighbouring properties. But how much does this invasive species affect property values in general? And why does it have such an impact on home valuations? Let’s take a look at how Japanese knotweed devalues property and how to deal with it in your own backyard.

What is Japanese Knotweed?

Japanese knotweed is a type of weed that can have negative effects on land, property and surrounding areas. The weed spreads quickly and can even damage properties in which it grows. It’s important to understand how Japanese knotweed will devalue your home before you decide to purchase a new home with it on.

Japanese knotweed (Reynoutria japonica) has been dubbed the worst weed in the UK by the Royal Horticultural Society, owing to its tenacity and the difficulty of eradicating it once it takes hold in a garden or property. Not only does it pose an aesthetic problem, but it’s also responsible for devaluation of properties when real estate prices are assessed to factor in its presence as either a potential risk or actual threat to nearby homes and buildings. This article explores how Japanese knotweed causes property devaluation and what can be done about it…

Signs of Japanese knotweed

Japanese Knotweed is quite distinctive and easily recognised once you’ve seen it once, you can pretty much identify it at all times. Knotweed has a distinctive rounded heart shaped leaf and thick stems that typically grow 6 inches per day in the UK throughout the summer.

You can check our Gallery through the seasons to see what the invasive weed looks like all year round:

Why it’s important to get rid of it

Although knotweed can’t cause any direct harm to your health, you may want to keep it away from your home if you care about how much your house is worth. According to a study published in 2013 by Nottingham Trent University, knotweed infestations can reduce a property’s value by as much as 15 percent. Depending on the size of the infestation and its proximity to buildings, it could render a property unsellable.

Knotweed will only keep growing and spreading so to ignore it could be extremely detrimental to your property and your pocket. If you allow Knotweed to spread from your land to a neighbour’s land or into the wild, it is a criminal offence and can carry a heavy fine and you could also end up with a claim against you which could run into tens of thousands.

How to get rid of it

Because Japanese knotweed can be difficult to control, chemical treatment will be necessary. Several specialist herbicides are available that work well with Japanese knotweed, such as glyphosate (Roundup), triclopyr (Weedol), imazapyr (Pursuit) and aminopyralid (Milestone). These are systemic herbicides, meaning they need to be taken up through plant roots or stems to have an effect; cutting them down will not help. A specialist treatment firm knows how to do this properly and it usually takes a visit every 3 months for 3 years to get a full treatment delivered.

An Actionable to Do List

First thing is getting your Knotweed formally identified by the Japanese Knotweed Agency, and where positive, request a FREE Onsite Survey and you’ll get a full report to show the locations of the crowns, age, route of growth, lots more information and a quote for a treatment plan that comes with an Insurance Backed Guarantee.

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How to Claim for Japanese Knotweed Trespass

If you’ve found Japanese knotweed growing on your property and don’t want it there, you may need to take legal action against the owner of the land where it has grown. This guide will teach you how to claim Japanese knotweed as trespass, so you can get your property back to full health and full value.

What is knotweed?

Knotweed or Japanese Knotweed is an invasive plant species which was brought to the UK in the early 1900’s as a decorative plant, unbeknown that it spreads like wildfire and can cause damage to property and amenities. Knotweed ryzomes (root system) and root growth can grow vigorous and can even grow through tarmac, concrete, water pipes, sewer pipes and can get into property foundations and cause havoc.

Knotweed can grow up to 8 inches a day in the summer and grow as tall as 12 feet high. The stems grow thick like bamboo and small stems grow from the main stems and grow a thick bush of leaves and even flowers through August and September.

What does trespassing mean?

If something from another person or property comes on to your property or land without your knowledge or consent, that is considered to be trespass. The fact that Knotweed has come from another parties land on to yours, and causes devaluation and other problems and can cost you money to put right, this is a recoverable trespass issue.

What are the options to resolve this issue?

If Knotweed is coming from a neighbour, the best approach in our opinion is to speak with your neighbour and try and get an amicable solution between you both. A survey and treatment plan with an Insurance Backed Guarantee will ultimately help both of you. If the Knotweed can be seen to be coming from your neighbour to your land quite obviously, your neighbour may agree to pick up all the costs. This is something hopefully as neighbours you can sort out.

If your neighbour doesn’t listen to your friendly request, you should put it in writing and allow them a small amount of time to get some resolve. Knotweed will only grow and spread if it is left and that will be worse for everyone.

If the Knotweed is coming from a commercial neighbour like the railway or council land or a commercial enterprise, report it formally so you have a record. Many times we see that although reported, the commercial entity doesn’t take it seriously enough or carry out proper treatment, then the problem again will only worsen.

The fact that Knotweed will not go away on its own, and a typical treatment plan with an Insurance Backed Guarantee can cost a few thousand pounds, you need to ask yourself should you pay for it if the neighbour is at fault? Then you need to think about any damage to your property and any devaluation because of the presence of Knotweed, and ask if you are happy with that or want to take action to protect your own asset.

If you decide to make a claim against the neighbour land owner, you can typically do this on a No Win No Fee. You should be able to recover the full cost of a treatment plan and force your neighbour to treat the Knotweed on their land to ensure it doesn’t come back again. You should also be able to claim the cost of the Insurance Backed Guarantee, and cash compensation for the devaluation of your property because of the presence of Knotweed. This may be an average of 10% of your property value, so a £200K property should start a claim for £20,000 plus treatment plus guarantee and maybe some additional compensation for inconvenience.

Which option should I choose?

The choices are really down to you. As your house and property is usually your biggest asset, it is important that you take this seriously and probably that you seek expert legal support to ensure you are fully protected.

How much will it cost me?

Japanese Knotweed Agency offer a FREE – WITHOUT OBLIGATION On-site Survey anywhere in England & Wales, which will give you all of the information you need to make a decisive way forward. The Survey Report will give you information on where the Knotweed has travelled from, its age, all identified crowns and growth areas, any potential damage caused by the Knotweed, and will also report on up to 58 other invasive weeds if any of those are present.

Your Survey Report will also come with a full quotation for treatment and a 10-year Insurance Backed Guarantee that if any Knotweed comes back after the treatment and within 10-years, it will get treated for free under the guarantee.

The Survey and report are 100% FREE and WITHOUT OBLIGATION

With that information you can then decide how to proceed and whether to move forwards with any legal claim. The options are then yours with detailed information at hand.

Request your FREE Onsite Survey here:

When should I claim Japanese knotweed as trespass?

As above, if you are friends with your neighbour and the Knotweed is coming from their land to yours, it may be best to speak together and try come up with an agreement.

If the neighbour doesn’t take notice or take action, the Knotweed will only get worse week by week, so you shouldn’t wait too long before taking action, whichever route you choose.

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