Japanese Knotweed Treatment Methods – Pros and Cons
Guest post by Michael Yau of Knotweed.co.uk
When it comes to Japanese Knotweed Herbicide treatment there are 3 main options.
- Spraying
- Stem Injection
- Weed Wiping
Spraying
This would involve spraying the Japanese Knotweed with herbicide to eradicate the plant. Although speedier than the other two methods it does contain one disadvantage. Spraying the herbicide in windy or wet conditions should not be done as it will not work and the chemical “mist” can easily drift into non-target vegetation and rivers, lakes, ponds and other watercourses if nearby. (A special licence is required to spray near water). If you do spray herbicide near water sources such as lakes and ponds then you will need to contact your local environmental agency to get permission. There is an alternative if it is raining or there is a nearby water course.
Stem Injection
Unlike spraying where the herbicide is sprayed onto the leaf surface of the knotweed, stem Injection as the name suggests works by injecting the stem of the plant with a concentrated dose of herbicide. Although more time consuming than spraying, it does offer advantages. Firstly the risk of herbicide drift on to non-target vegetation and water sources is eliminated. Second, stem injection is not weather dependent. Heavy rain can wash away the herbicide. Thirdly stem injection often proves to be more successful in the eradication of knotweed. The main disadvantage is that stem injection is slower because each stem needs to get injected and doesn’t offer the coverage spraying offers.
Weed Wiping
Weed wiping is when a hand held weed wiper/sponge is used to apply the herbicide onto the leaf surface of the knotweed. Like stem injection, it does not affect neighbouring vegetation and water sources. It is an alternative option to the knotweed injection when the stems of the knotweed are not thick enough. Weed wiping is more time consuming and is only practical on smaller infestations.
The length of treatment regardless of whether it is spraying, stem injection or weed wiping is normally 2 years and an additional 3 years annual treatment/monitoring to make sure there is no knotweed re-growth. That means there would be in total 5 years of treatment. Clients can also purchase a 10-year programme where there is 2 years treatment, 3 years monitoring and an additional 5 years guarantee. During the guarantee period if Knotweed does grow back then it will be treated under the guarantee. For most mortgage lenders they will want a least a 10-year programme or excavation.
Having Japanese Knotweed present on your property could severely affect the value of the property. How much depends on the severity of the knotweed problem. While most lenders will agree to lend on a property with Japanese Knotweed, they want a programme of treatment that will deal with the problem. In most cases it is the seller who will bear the cost of treatment.
In deciding whether to undertake treatment or excavation/removal a knotweed survey is normally carried out to determine the severity of the infestation. In one case, a couple who lived in a house for only a month then discovered Knotweed growing in the garden and eventually inside the property. The property initially having a value of £305,000 fell to just £50,000. In another case, a 91-year-old woman has Japanese Knotweed growing on a piece of land near her garden. The house was initially valued at £80,000 but after knotweed was discovered the value fell to £45,000.
In these severe circumstances, spraying, stem injection or weed wiping may not be enough to control the invasive weed unless the homeowner is planning to live there and keep the knotweed under check. If the home owner wish to sell the property and the infestation is significant (only a knotweed survey can determine this) then knotweed excavation may well be the best option as excavating and removing the knotweed is the only practical option to remove the Knotweed infestation permanently. Once the Japanese Knotweed has been removed then the property should restore back to its original value. One method is to get an idea of the value before and after treatment/excavation and then decide whether herbicide treatment is more viable or excavation.
If you are the property owner it is wise to book a Knotweed Survey even if you are not thinking of selling. This will eliminate a lot of grief when the time comes to sell your property as Knotweed has already been identified and you can make plans for treatment. When consulting a Japanese Knotweed company ensure they are reputable and accredited by the Property Care Association (PCA) and that the survey includes a Knotweed Management Plan (KMP). Also, make sure that the Knotweed Management Plan includes a detailed scale drawing showing the size and location of the Knotweed affected area and that it indicates the level of risk as defined by the RICS (Royal Institute of Risk Chartered Surveyors) Table. This is particularly important in the survey as you will need to know the severity of the Knotweed infestation and where it‘s located. The closer the infestation is to the property the higher the risk. In many cases, it is the RICS Risk Table that determines whether herbicide treatment is more appropriate or excavation. If you have Knotweed on land that has an extension or you are planning to landscape that piece of land, then the knotweed contaminated soil has to be excavated before you can build on it.
Treating Japanese Knotweed is best done by the professional specialist companies and advice from a specialist like Japanese Knotweed Ltd to get the correct treatment is prudent. Having a Japanese Knotweed surveyor assess the surrounding area and prescribe the correct course of treatment is the best way to deal with the invasive plant.
If Japanese Knotweed is within the footprint of a proposed extension/building or landscaping work then herbicide treatment may not be practical. In that case, the other option is excavation and removal.
If you have Japanese Knotweed and need an initial consultation please visit www.japaneseknotweed.co.uk
The Property Voice Insight from Richard Brown
Problems in property can come in many guises - they can be both a threat and an opportunity. The key to our long-term sustainability as property investors has to start with reducing the potential threats as far as possible. Opportunities can then be capitalised upon to accelerate our results and progress.
One such threat to an existing property is Japanese Knotweed, which we have featured previously on our Blog here. The first step to defend our position is to avoid taking on a problem that we cannot deal with in the first place...be it with an existing property asset we hold or a potential new one. Checking for the presence of Knotweed then is a very good idea. Surveys and even careful initial inspections can help to reveal a potential problem. With an existing property, make sure you keep an eye out with regular garden maintenance and / or inspections and if in doubt, call in a specialist to give an assessment. The same goes with a new property acquisition, particularly if we are not knowingly taking on a property with an existing Knotweed problem. As Michael highlighted, the consequences in terms of mortgagability (or rather not) and property value can be VERY significant to live with. However, there are some effetive Japanese Knotweed treatment methods as has been highlighted, which should help to calm the nerves a little if we do discover it.
Flipping the coin a little and looking at this as a potential opportunity instead. If we can identify a Knotweed problem in a property before we acquire it, then it will first of all scare a lot of potential buyers away...that's the first aim...eliminate the competition. Next, given the issues around desirability and in particular the potential length of time costs of Japanese Knotweed treatment costs, along with the consequential mortgagability issues, it can lead to heavy discounts on the purchase price. If we look at the two examples cited in Michael's article, in one case from a buyer's point of view, the potential uplift in value was around £250,000 or 500% of the property purchase price / value; whilst in the other, possibly a more realistic £35,000 uplift at 78%. These are very significant potential ROIs for fixing a very treatable problem. Do keep in mind, however, that the property may have to be bought using cash initially rather than finance, so it could tie up cash resources for a time.
Whether we are looking to defend against a potential threat, or take advantage of a potential opportunity, understanding more about the problem of Japanese Knotweed and the potential treatments will assist us. I would like to thank Michael Yau from Japanese Knotweed Ltd for sharing his experience and insights on Japanese Knotweed treatment methods with us on the subject, therefore.