Japanese knotweed is one of the most dangerous weeds in the UK. The reasons for this are simple. It is extremely fertile (able to regrow from a tiny bit of rhizome), fast-growing (able to grow at a rate of 10cm-20cm per day) and tenacious (able to grow through anything, poor soil, tarmac, concrete etc.).
So, if you don’t move quickly, it (Japanese knotweed) will overwhelm your garden. Then move on to the rest of the property, growing through and destroying everything in its path. According to experts, a Japanese knotweed infestation can reduce the value of a property by 5-15%.
So, how much will it cost to stop this? How much does it cost to remove Japanese knotweed? The answer depends on the size of the affected area and the removal method. However, for the average-sized garden, Japanese knotweed removal costs £1,000-£12,000.
That’s much higher than the average weed removal project, but Japanese knotweed is not like the average weed. Its removal process is also unlike the removal process of the average weed. This article will show that.
It will show everything you need to know about removing Japanese knotweed. So that you can fix the problem once and for all. We will cover the removal methods, factors that affect removal costs, hiring tips, etc.
How much does it cost to remove Japanese knotweed?
Japanese knotweed removal prices
| Removal method | 50m2 or smaller | 50m2-100m2 | 100m2-500m2 | 500m2-1,000m2 |
| Herbicide treatment | £1,000-£3,000 | £3,000-£5,000 | £4,000-£6,500 | £5,000-£10,000 |
| Sifting and screening | £2,000-£5,000 | £5,000-£10,000 | £15,000-£40,000 | £40,000+ |
| Excavation with burial on site | £5,000-£15,000 | £10,000-£20,000 | £18,500-£35,000 | £30,000-£75,000 |
| Full excavation and disposal | £5,000-£20,000 | £14,000-£39,000 | £35,000-£120,000 | £100,000-£200,000 |
| Excavation and root barriers | £2,000-£5,000 | £5,000-£10,000 | £15,000-£40,000 | £40,000+ |
| Onsite relocation and herbicide | £5,000-10,000 | £11,000-£20,000 | £12,500-£20,000 | £18,000-£30,000 |
The supply costs of removing Japanese knotweed
| Removal method | 50m2 or smaller | 50m2-100m2 | 100m2-500m2 | 500m2-1,000m2 |
| Herbicide treatment | £900-£2,700 | £2,800-£4,500 | £3,700-£5,900 | £4,500-£9,000 |
| Sifting and screening | £1,900-£4,800 | £4,800-£9,500 | £14,700-£39,300 | £39,100+ |
| Excavation with burial on site | £,4,900-£14,400 | £9,800-£19,500 | £18,200-£34,300 | £29,000-£74,000 |
| Full excavation and disposal | £4,200-£19,700 | £13,800-£38,500 | £34,700-£119,300 | £99,600-£199,00 |
| Excavation and root barriers | £1,900-£4,700 | ££4,800-£9,500 | £14,700-£39,300 | £39,000+ |
| Onsite relocation and herbicide | £4,900-£9,700 | £10,800-£19,500 | £11,100-19,300 | £17,600-£29,100 |
The labour costs of removing Japanese knotweed are about £20-£50 per hour. However, that’s nothing compared to the supply costs, which usually make up about 80-90% of total expenses. You can see this in Table 2.
Any weed removal service will probably want to first inspect the site before providing a quote. During this inspection, they will confirm the identity of the weed and the severity of the infestation. Then they will recommend a management plan. This plan will contain a proposal for removing Japanese knotweed within legal restrictions for your area and the weed.
What are the factors that determine the cost of removing Japanese knotweed?
Japanese knotweed removal costs will vary depending on the following factors.
The size of the affected area
The larger the infested area, the more resources it will take to complete the project. By resources, we mean time, supplies, working hours, and even number of workers. You can see this clearly in Table 1. For each of the 6 Japanese knotweed removal methods, the costs increased with size.
Accessibility
The more accessibility issues your weed removal service faces, the more time and effort it will take to complete the project. Therefore, they will probably want to charge more. By accessibility issues, we mostly mean “the ease of moving equipment and supplies”.
However, in cases of Japanese knotweed treatments that require off-site disposal, it could also mean “the accessibility of disposal sites”. Expect to pay higher rates if there is no viable disposal site in your area, or if the ones available are costly.
The Japanese knotweed removal/treatment method
Table 1 shows how the treatment method determines Japanese knotweed removal cost. Herbicide treatment is the most affordable, while “full excavation and disposal” is the most expensive.
That’s because the latter requires more time, effort and supplies. However, it’s a case of “you get what you pay for” because the latter is also the most effective of all Japanese knotweed treatment methods.
Your geographical location
This affects Japanese knotweed removal costs in two ways. Firstly, places like the Southeast and big cities have a higher standard of living. Therefore, most projects usually cost more, Japanese knotweed removal is no exception.
Secondly, most weed removal services will want higher rates if they are coming from afar. Some may even ask for a minimum call-out fee. So, expect distance to also affect the cost of removing Japanese knotweed.
What are the methods used for removing Japanese knotweed?
Technically, there are two main methods used for the removal of Japanese knotweed infestation. These are excavation and herbicide treatments. Every other method is a variation of these two.
Herbicide treatment
This usually involves spraying or injecting herbicides into the Japanese knotweeds. The herbicide needs to be applied at intervals. So herbicide treatment often takes up to 5 years or more.
Compared to the other Japanese knotweed removal methods, herbicide treatment is the least expensive. However, it is also the least effective. Many weed removal services don’t even consider it a viable way to treat Japanese knotweed. They see it as more of a management method.
This is because herbicides don’t exactly fix the problem. They only make Japanese knotweed dormant. The problem will come back in a few decades. Plus, herbicide treatments also endanger the other plants in your garden, the environment in general, animals and humans.
Sifting and Screening
Also known as picking and sorting, it involves excavating and screening affected soil to remove Japanese knotweed materials, such as rhizomes and seedlings. These knotweed materials can then be buried or burnt while the screened soil returns to the ground.
Basically, it is about cleaning up (removing contaminants from) the affected soil, but there lies the problem. Some Japanese knotweed materials could get through and kickstart the infestation again. Despite this risk, sifting and screening is an effective way to control Japanese knotweed, albeit a time consuming one.
Excavation with burial on site
Also known as onsite relocation, this involves full excavation and burial of the affected soil. Unlike sorting and screening, there is no attempt to remove contaminants. Instead, the entire contaminated soil is dug up and buried. In this case, it is buried on site.
This treatment is much more disruptive than the last two. However, it is also much more effective. The affected area must be excavated more than 3 metres deep and 7 metres in all four directions. That’s how much the roots of Japanese knotweed go to the sides and depth. The contaminated soil must also be buried at least 10 feet deep.
Full excavation and disposal
Also known as “dig and dump” or excavation with offsite relocation, this treatment method is exactly like the last one. The only difference is that the excavated (contaminated) soil isn’t buried on site. It is instead buried in a landfill, at least 5 metres deep.
Whichever mode of disposal is chosen, the contaminated soil must be treated as controlled waste. Because it can trigger another outbreak of Japanese knotweed.
Excavation and root barriers
Also known as “reduce dig and root barriers”, this is another variation of the excavation method of treating Japanese knotweed. Only this time, the excavation is on a smaller scale. The affected area is not completely dug up, at least not in the same scale as the first two excavation methods.
This means that some Japanese knotweed materials could remain in the soil. That’s where the root barrier comes in. It is laid over the affected soil to prevent remnant Japanese knotweed material from spouting new growth. Some weed control services may also include sifting and screening to increase the odds of ending the Japanese knotweed problem once and for all.
As for the excavated (contaminated) soil, it is disposed like before, by onsite or offsite burial.
Onsite relocation and herbicide
This method combines “reduced dig” and herbicide treatments. It involves first using herbicides to weaken and kill the Japanese knotweeds. Then, excavating and burying part of the affected soil onsite.
It is an effective and decently priced way to deal with a Japanese knotweed infestation. Just be aware that, like the other “reduced dig” method, some knotweed materials could scale through the removal process.
How do I find a qualified and affordable Japanese knotweed removal service?
You must hire a qualified and licensed professional if you want to resolve this Japanese knotweed problem once and for all. Hiring the wrong person could mean you will have to go through the entire process again in a few months. It could even lead to issues with the authorities. That’s why you need to consider the following tips.
- Ask trusted colleagues, neighbours, friends and loved ones for recommendations
- Check local and reliable tradespeople
- If you find a weed removal service over the internet, ensure they have a good reputation and reviews
- Make sure they have enough experience with Japanese knotweed. In fact, it is better to choose a Japanese knotweed specialist
- Ensure they have Public Liability Insurance
- Ensure they offer some sort of Insurance-Backed Guarantee (IBG). This basically means they will do an annual site visit and redo weed removal completely free if the infestation restarts within a specified time.
- Get quotes from 3 to 5 good Japanese knotweed removal services
- Get a full breakdown of what the service entails
Can I remove Japanese knotweed DIY?
Yes, but the more appropriate question is “should you?”. We have already established that Japanese knotweed removal is a complex and time-consuming process. There are also financial and legal consequences for failed or improper disposal of Japanese knotweed material. Plus, you could mistakenly spread the infestation to other places.
So, although you can treat Japanese knotweed yourself, saving money in the process, it is better to hire a professional. Even if you decide to take on the job yourself, consult a professional to inspect the site and recommend a removal method.
Conclusion
There is a reason people refer to the Japanese knotweed as “demon weed” or “devils bamboo”. It’s an almost unstoppable weed that affects about 5% of all homes in the UK. But, it can still be treated, as long as you use a thorough method and move quickly.
If you delay, the infestation will get worse. Therefore, removal will be harder and costlier. So, try to hire a specialist as soon as possible, and ensure they offer an Insurance-Backed Guarantee (IBG).
FAQ
How do I identify a Japanese knotweed?
It has creamy white flowers; shovel-shaped leaves with red veins; and a tough, fleshy and hollow (bamboo-like) stem. In winter, the flowers turn yellow and the leaves drop.
What is the best method for treating Japanese knotweed?
It depends on the severity of the infestation, and the size and characteristics of the affected area. So, it’s better to let a Japanese knotweed specialist survey the site and recommend a treatment.
However, soil excavation is the best treatment for Japanese knotweed. It is an effective and natural control method without side-effects.
What happens if I decide not to remove Japanese knotweed?
It will continue to spread and grow, overwhelming your entire property and neighbouring lands. This will reduce the value of all the properties involved, which means you are legally responsible to the property owners.
Finally, you could also get in trouble with the authorities for allowing a controlled plant to spread.
How can I get in trouble with the authorities for allowing Japanese knotweed to spread?
There are at least 3 legislations that allow a local council to force any property owner to control Japanese knotweed or penalise them for allowing it to spread. These legislations include the “Wildlife and Countryside Act 1981 section 114“, the “Anti-Social Behaviour, Crime and Policing Act 2014” and the “Town & Country Planning Act 1990 section 215“.
The penalties include a £5,000 fine or up to two years in prison. However, these are intended for people who allow Japanese knotweed to spread, knowingly or unknowingly. No one can penalise you for having it on your property.
What do I need to know about buying, selling or mortgaging a property with Japanese Knotweed?
- Buying: the seller has a legal responsibility to tell you about the Japanese knotweed problem. However, you also need to organise a professional survey before buying a property. This will save you from making bad purchases.
- Selling: You have a legal responsibility to tell the buyer that there is a Japanese knotweed on the property. If not, you could get sued.
- Mortgaging: Mortgage lenders won’t want to mortgage the property unless the Japanese knotweed problem is not severe and you already have a management plan in place.
