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Japanese Knotweed Removal on Waterways

Table of Contents

The methods for treating and removing the invasive plant Japanese knotweed include herbicide chemicals and excavation using machinery. The choice of treatment is not just about the immediate eradication of Japanese Knotweed; it involves careful consideration of the surrounding ecosystem.

The Impact of Japanese Knotweed on Waterways

Japanese knotweed is a major threat to UK waterways as an invasive plant species. As an invasive species that spreads quickly, it can grow 3 meters in 3 months and outcompete native plants. Here’s how it affects our waterways:

  • Biodiversity Loss: It creates dense thickets that block out sunlight and deplete resources for native plants, threatening local habitats. This aggressive growth also harms other plants by monopolizing nutrients and space.

  • Structural Risk: Knotweed rhizomes can penetrate concrete and tarmac, putting adjacent land and water defences at risk.

  • Ecological Imbalance: Spreads from fragments of its rhizomes, even tiny bits can regrow, and take over native vegetation.

  • Legal and Financial Burden: Disposal of material with knotweed has to be done according to strict regulations to prevent further spread, and costs land management and legal liability.

Removing along waterways requires knowledge of Japanese knotweed’s life cycle and having experience and knowledge of mechanical removal methods. Any contaminated soil or plant waste must be disposed of at a licensed landfill to get rid of it completely. Getting rid of this invasive weed is key to protecting our waterways’ integrity and biodiversity.


Fill in the form below, attach your pictures and we’ll let you know if the plant in your picture is Japanese Knotweed.

Japanese Knotweed Control Methods


Herbicides applied directly to the weed via leaf wiping, stem injection or knapsack spraying target the weed systemically. Glyphosate is the most trusted chemical in this fight; it’s known for its effectiveness to treat Japanese knotweed.

The window for chemical control is April to September; this coincides with the plant’s growth cycle. This is when the herbicide is absorbed during active growth when it’s most effective. But it must be applied by someone with the relevant qualifications as the area is near water. By doing this, you can stop the Japanese knotweed in its tracks and protect the native ecosystem.

Glyphosate, a potent non-selective herbicide, is most frequently employed due to its effectiveness. However, its application should be meticulously targeted to safeguard other plant life—a method achieved using cloths, rollers, brushes, or sponges that confine the chemical to the leaves and stems of the invasive weed. Additionally, professionals might opt for direct stem injection of chemicals for efficient treatment, using specialized injectors to minimize the risk of affecting the ecosystem.

In situations where chemical treatments are unsuitable or to secure lasting results, excavation becomes a prominent choice.


If you’re looking for a non-chemical solution to your Japanese knotweed problem, mechanical control is an option. Excavation, done properly, removes the whole plant including its extensive knotweed rhizome system. 

This can result in two outcomes; the material is taken to a licensed landfill site following strict guidelines or it’s managed on site in a designated waste management area or burial pit.

Unlike the ‘dig and dump’ method, a combination of excavation and onsite treatment is more considerate to the environment, as favoured by the Environment Agency. Once extracted, removed knotweed can be buried at 5 meters deep or contained in a barrier cell at 2 meters deep.

 These methods use robust root barrier systems not the flimsy weed membranes to comply with environmental regulations.

Excavation also meets ecological requirements and avoids chemicals. After treatment, vigilance is key: the site must be monitored regularly to prevent regrowth and keep the waterway healthy.

Impact on Native Vegetation

The presence of Japanese Knotweed alongside waterways severely alters local ecosystems. It dominates environments with dense thickets, outcompeting native vegetation and reducing biodiversity. This invasive species can also harm other species when herbicides are used improperly. The dense root systems also contribute to bank erosion which, in turn, increases the risk of flooding—a particular concern along watercourses. Urban areas face the additional challenge of structural damage as the powerful growth of Japanese Knotweed stems can penetrate and disrupt materials like asphalt.

Japanese Knotweed spreads through the dispersion of its root pieces, a process greatly facilitated by water. Acknowledging the economic and environmental costs of this invasive species underpins the need for its diligent management and removal from waterways.

Stopping the Spread

Stopping Japanese Knotweed spreading is just as important as removing it. This invasive weed can spread through direct rhizome extension or plant fragment regeneration, including the Japanese knotweed rhizome.

Early detection and control is key to limiting the damage of Japanese Knotweed and reducing environmental and economic impact. For effective prevention, regular monitoring and responsible site management is the key to preventing re-growth and further invasion into native habitats.

Disposal of Knotweed Material as Controlled Waste

After Japanese Knotweed removal, it’s important to dispose of the material properly as it is classified as controlled waste. Disposal options are to move the material to approved landfill sites or use incineration facilities with the necessary permits. All transportation of knotweed waste must be done by licensed waste carriers and the disposal must be notified to the relevant authorities, like the Environment Agency.

Companies specializing in the treatment of invasive species must adhere to industry accreditations and memberships, ensuring that disposal operations are compliant with all legal and environmental guidelines. It is worth noting that incineration or burning of the plant may not be sufficient to eliminate it completely; hence, recognized best practices such as off-site disposal or secure burial should be followed to guarantee the successful mitigation of Japanese Knotweed.

Monitoring and Maintenance

The success of controlling Japanese knotweed and other invasive plants is all about monitoring and maintenance. Regular monitoring is key to catching new growth early which means less cost removals down the line.

Maintenance practices such as follow up treatments and reintroducing native species helps to keep waterways clear of Japanese Knotweed. It’s through these ongoing efforts that we can protect natural environments from the invasive and maintain biodiversity and ecosystem balance.

Regular Inspections

If you own land near waterways, regular inspections are key to prevention. Japanese Knotweed was initially introduced to the UK as an ornamental plant from Japan in the 1840s, prized for its bamboo-like appearance. Areas near waterways are vulnerable to Japanese Knotweed, so site surveys are essential to detect its presence. These are crucial for property transactions near waterways. Not detecting and disclosing Japanese Knotweed can result in severe legal consequences and big legal bills.

And screening soil before use in landscaping projects is vital to stop introducing this invasive weed. Using reputable soil suppliers and insisting on soil being knotweed free is essential – an ounce of prevention here will save a world of trouble.

Follow-up Treatments

Japanese knotweed treatment follow-up treatments are just as important as the initial treatment. Chemical controls, such as expertly applied herbicides, work long term with repeated treatments to get both foliage and rhizomes.

Excavation is a quicker solution but comes with its own follow up. Whether the material is removed to a licensed landfill or managed on site, monitoring for regrowth is key. Soil screening can be used as a less invasive option, separating contaminated soil and preserving the good soil – so you don’t waste and can dispose of sustainably.

The Role of Weather Conditions

Japanese Knotweed really comes into its own in environments that are both warm and wet. This tough invader doesn’t shy away from mild winters, holding on until the weather turns in its favor. From the warmth of mid-spring to the cool embrace of mid-autumn, that’s when Knotweed truly bursts into life. And let’s talk about summer — it’s not just growing; it’s as if it’s on a sprint! Averaging a growth of about 2-4cm daily, this plant doesn’t stop there. On its best days, under just the right sunny skies, it can shoot up an impressive 10cm in a single day.

Japanese knotweed really shows its stubborn side by how aggressively it spreads. It’s strong enough to break through concrete, pavements, and driveways, and can even jeopardize the stability of buildings. This really highlights why it’s so important to keep tabs on how it grows, especially with how it changes with the weather. However, there’s a bit of a break during winter when the plant’s above-ground parts die off, leaving only the roots behind. These roots cling onto life, quietly waiting for spring to spring back into action.

Effectiveness of Control Methods

When dealing with Japanese Knotweed, it’s essential to act quickly and use effective Japanese Knotweed treatment methods. Excavation is a primary control strategy, especially in urgent situations. This thorough approach involves completely removing the unwanted plant, including its extensive root network. The excavated Knotweed can then be taken away from the affected area or placed in a designated waste management area to prevent further spreading.

One way to tackle the problem is by turning to soil screening. This method focuses specifically on soil that’s been taken over by Knotweed. It works by sorting out and getting rid of the weed contaminants from the soil. What’s great about this approach is that it allows the cleaned soil to be reused, whether for beautifying landscapes or development purposes. Plus, it helps avoid the need to dump massive amounts of soil into landfills. For those looking for another option, using chemical treatments based on glyphosate sprays is another effective strategy for managing knotweed infestations.

Getting rid of Japanese Knotweed isn’t a quick fix—it’s a slow, careful battle that can take 2 to 3 years. We’ve got to be diligent, using measures like digging it out or treating it with chemicals. It’s super essential not just to keep our environment and buildings safe but also to make sure we’re following the law, especially when it comes to selling property or getting a mortgage.



A tried and tested methodology used on hundreds of sites across the UK.

Using the screening method, the Japanese knotweed rhizome material is separated from the soil material. The Japanese knotweed material is then either transported to licensed landfill at a much lower disposal rate or incinerated on site using a D6 exemption from the Environment Agency or Natural Resources Wales.

The cleaned soils can then be reused in locations away from any construction, normally in soft landscaping areas.

This can reduce the landfill & backfill requirement costs significantly and can also help to reduce the carbon footprint on site due to reduced vehicle movements to landfill.


Knotweed Services can provide a biosecurity operative to supervise any excavations and movement of soils containing Japanese knotweed on site. 

As part of these measures, we can provide a biosecurity boot wash and machine-washing area installed in an area at the entrance to the site.
We will provide all toolbox talks for the main contractor on site, which will be signed by all contractors involved in the operation on site.

We can provide temporary geotextile barriers if required in areas to maintain the biosecurity on site.

Once the works have been completed, we will provide the client with a full biosecurity report.

This method can be used in conjunction with other treatment methods on site.

Commercial Japanese Knotweed Excavation


This treatment method is ideal where time constraints are present and there’s no other option other than to remove both the Japanese Knotweed and contaminated soil to a registered landfill.

By removing all traces of the infestation quickly, this offers a rapid solution to your problem and allows your commercial project to begin groundwork’s almost straight away. When time is of the essence, there is no quicker Japanese Knotweed removal/treatment method.

Any waste taken off-site will be done so with a licensed waste carrier to a suitably authorised landfill site.

Japanese Knotweed Cell Burial


Cell burial comprises of moving Knotweed contaminated soil from one location on site, burying it in an excavated pit which is lined with a root barrier membrane, in a different position on the site.

The burial requirements for Japanese Knotweed are as follows:

  • The Environment Agency recommends that the top of the burial cell should be a minimum of 2 metres below ground level.
  • The overall depth of the burial pit should be in excess of 5 metres deep. All root barrier seams are welded together forming an encapsulated cell from which the Japanese Knotweed cannot escape. Clean soil is then used to backfill on top of the cell.
  • To prevent accidental disturbance of the burial site, it is recorded on all site plans and future land owners should be made aware of the location.


Bunding is the method of relocating contaminated Japanese Knotweed soil to a different area of the site being treated. A bund is a shallow area of the contaminated soil, typically 0.5m deep.

The bund can either be raised, on top of the ground, or placed within an excavation to make the surface flush with the surrounding area.

The purpose of the bund is to move the Japanese Knotweed to an area of the site that is not used. This ‘buys time’ for treatment that would not be possible where the Japanese Knotweed was originally located.


At Knotweed Services we can provide the client with bespoke treatment plans depending on the locations of the Japanese knotweed. 

These plans can work in conjunction with other methods of treatment where access is limited to pedestrian movements i.e., embankments or existing pathways within a site.

This will normally consist of up to 3 visits per annum to apply herbicide by either foliar spray technique or stem injection during the growing season over a period of 3 years, with a monitoring period of 2 years thereafter.

We would select the appropriate herbicides depending on the surrounding foliage or environmental constraints.

After each visit a full treatment record would be provided with photos showing the progress of the works and then an annual report.

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