Despite claims by some companies, Japanese knotweed cannot be killed or eradicated by herbicide application alone. It can be controlled via herbicide treatment or fully removed from a property by excavation.
Often, the most cost-effective method of controlling Japanese knotweed is a Herbicide Treatment Programme (HTP). An HTP involves a schedule of methodical and carefully managed Japanese knotweed treatments, where correct use of chemical over a sustained period will exhaust the plant and prevent the spread of Japanese knotweed. However, it will not remove the plant’s rhizomes (roots) from the soil. Our excavation methods fully remove the knotweed from the ground. Our experts ensure complete Japanese knotweed removal, because leaving as little as 0.7g of rhizome could mean that knotweed grows back again.
Does Diesel Kill Japanese Knotweed?
Contrary to popular belief, diesel does not kill Japanese knotweed. Whilst it may look like it is doing damage by distorting the top growth, the rhizomes in the soil will not be affected. This means, after a certain period, new top growth will appear and grow just as prominent as before.
Even if you cut the stems and pour diesel into the top, the underground rhizome system will still regrow. In addition to this the surrounding soils will be polluted with risk of diesel, which is toxic to humans and animals, soaking into the groundwater. Most importantly this or any use of diesel other than its intended purpose is completely unethical and, in many situations, illegal.
Will Bleach Kill Japanese Knotweed?
Bleach is another chemical that is ineffective and causes other additional problems. Bleach is a useful household product for cleaning and disinfecting, but is not made to be a weed killer, despite its corrosive chemicals.
Cutting stems and pouring bleach down them will damage the top growth, but the rhizomes will not be affected. If bleach seeps into a pond or watercourse it’s highly toxic to aquatic life, and if it seeps into soils it can damage surrounding plants, causing more harm than good.
Burning Japanese Knotweed
Whilst burning Japanese knotweed may remove the top growth, it won’t have any effect on rhizome growth. The top growth will die back and the plant may appear to be dead, but the rhizome will be unaffected and will ultimately produce new above-ground stem growth.
So, burning knotweed will inevitably just leave a black patch of land on your property, which will eventually return to Japanese knotweed growth. If you only want to cut and remove the top stem growth, you can burn the knotweed, subject to local council bylaws, keeping all material and ash on-site; however, we recommend using a professional service such as our own, to properly remove and dispose of this extremely invasive plant.
Killing Japanese Knotweed with Vinegar
Neither vinegar or salt will help eradicate Japanese knotweed, and both are best used on your fish & chips.
Will Pulling Out Knotweed Stems Kill It?
Pulling Japanese knotweed from the ground will only provide a temporary solution. The rhizomes grow very deep and are unlikely to be removed by this activity. The rhizome WILL produce new growth. Therefore, you would not be removing the source of the problem and in addition, you would be creating knotweed waste (the pulled stems), where its disposal falls under the Environmental Protection (Duty of Care) Regulations 1991.
If you do decide to pull up the knotweed stems, we advise you to not remove the waste from site. Improper disposal of knotweed can cause further spread around your garden and elsewhere. Leaving any trace of knotweed waste on your compost heap may only cause it to regrow and spread further.
Once knotweed waste leaves your site or property, it becomes classed as controlled waste and must be carried by a company with an appropriate Waste Carriers Licence, issued by the Environment Agency (E.A.). The controlled waste must be taken to a landfill site licensed by the E.A. to receive and dispose of Japanese knotweed.
Mowing Japanese Knotweed
Moving, strimming or flailing Japanese knotweed is likely to significantly increase the risk of knotweed spreading across your property and onto neighbouring land. As well causing a further knotweed problem, it’s also an offence to plant, disperse or allow dispersal, or cause the spread of Japanese knotweed and other non-native invasive plant species listed under the Wildlife and Countryside Act 1980.
Additionally, you cannot dispose of knotweed waste at your local recycling centre or in your garden waste bin. You could receive a fine of up to £2000 or up to 2 years in prison.
How to Kill Japanese Knotweed with RoundUp
RoundUp is a brand name of a herbicide product, which uses the active ingredient glyphosate. There are also other glyphosate-based herbicide products. Glyphosate-based herbicides have been found to be the most effective at controlling Japanese knotweed. There are however many herbicide products that use glyphosate, and some are better than others.
RoundUp that can be bought from shops will not kill knotweed. If applied correctly, it might control its growth after successive treatments. For the best results with herbicide, it’s recommended to call us for a quote. We use high-grade safe herbicides applied at the correct time with the correct dosage, ensuring the most effective control possible. If using herbicide, you must always follow the government-regulated label on the bottle on how to use it. Read more about our herbicide treatments here.
Does Glyphosate Kill Japanese Knotweed?
Long term trials by the University of Swansea have academically proven that herbicide treatments alone cannot kill Japanese knotweed, but are effective at controlling it. The trial proved that glyphosate herbicide products were the best herbicides to use. Correct use of high-grade glyphosate-based herbicides can effectively control the plant and ultimately prevent the plant from producing above-ground knotweed growth.
The best time to apply the herbicide is during the summer or early autumn when the foliage can absorb the most nutrition into the rhizomes. Glyphosate works by being absorbed through the leaves and stems of an actively growing plant and translocating, or moving, through the plant and attacking the plants' rhizomes. It therefore needs to be applied while the knotweed is actively growing between spring to early autumn.
However, it’s unlikely the herbicide will translocate to every part of the knotweeds' rhizome system, meaning some parts stay viable and the knotweed will not be killed or eradicated. It can render the rhizome dormant, with no active growth, and unless disturbed, may stay dormant and controlled indefinitely.
Killing Japanese Knotweed with Lime
It has been suggested that a natural remedy for killing knotweed is lime, also called calcium carbonate (CaCO3). Lime can be used to neutralise acidic soils, as it’s an incredibly alkaline substance. This alkalinity makes lime dangerous and will injure humans or animals on skin contact, or inhalation.
Japanese knotweed has a very high tolerance of different soil types and is found growing in very acidic, neutral and alkaline soils. Therefore, adding lime to increase the alkalinity of soils will not stop Japanese knotweed growing. Large amounts of lime added to the base of knotweed may burn it, due to its high alkaline content. However, as with bleach, this may only result in damaging the above-ground stems and the rhizome will quickly generate new top growth.
Can You Kill Japanese Knotweed?
In short, Japanese knotweed cannot be killed and can only be controlled via herbicide treatment or removed via excavation by a professional knotweed company.
If your property or land is affected by Japanese knotweed, we can help. We are the UK's largest dedicated Japanese knotweed and invasive species treatment and removal company. Contact the UK’s trusted knotweed experts today to arrange a free survey.