The mere presence of Japanese knotweed on your land or property should be a cause of concern even at its initial stages of growth. Selecting the right professional weed killers for Japanese knotweed that will eliminate it for good is essential.

The more time you give it to grow and thrive on your property, the bigger the problem you have to deal with as time passes by. This weed plant causes unprecedented damage not only to the environment but also to the property and the biological diversity of an area.

On this footing, getting rid of Japanese knotweed should be a matter of earnestness whenever you spot the plant growing anywhere.

Although various methods have been recommended for eradicating this weed plant, experts across the board agree that the use of weed killers for Japanese knotweed works best in the removal and complete annihilation of this weed plant.

Choosing the right weed killer to do the job is critical when trying to eradicate Japanese Knotweed
Choosing the right weed killer to do the job is critical when trying to eradicate Japanese Knotweed

The reasons why herbicides are considered to be the best Japanese knotweed killer include:

  1. The ability to work both on the foliage (leaves and canes) of the plant together with the root system.
  2. The ability to deliver quick results within a very short period – many of the Japanese knotweed killers start showing results as early as 3 hours after application.
  3. Most of these weed killers have a non-restrictive use meaning that any person can readily purchase them from recommended workshops dealing with such products.
  4. The weed killers are also easy and safe to use based on the fact that each chemical comes with instructions on its application.

Notably, for any Japanese knotweed killer to pass the test of quality guarantee and maximum effectiveness it must have the following features:

  1. A good weed killer should have an active ingredient called glyphosate which should have a concentration of about 41% or more for good results.
  2. The weed killer must always act fast on the weed plant and show results within a short timestamp.
  3. The weed killer must be resistant to rainfall for at least the first few hours of its application.
  4. The weed killer should be relatively easy to use; the formula should be ready to use however if the weed killer is a concentrate, there should be clear guidelines on how to mix it properly.
  5. The weed killer should be able to act both on the foliage and roots of the weed plant effectively. The aim is to completely eradicate this nuisance weeds plant.
  6. The recommendable application method should either be sprayed directly into the Japanese knotweed or injecting it into the stem of the plant. However, experts advise that the former method should take precedence. 
  7. Ensure the weed killer has fewer effects on the surrounding environment. This is to say it should not be too harsh on the vegetation or plants.

Review of some of the best professional Japanese knotweed killers readily obtainable

This section will review the best weed killer for the eradication of Japanese knotweed among the various varieties that are considered the best when it comes to the removal of this highly invasive weed plant completely.

The list is not in a priority order but rather general guidance as to the most effective Japanese knotweed killer.


This is a no-mix formula that acts fast even on the stronger weeds that seemingly won’t go away. This weed killer delivers quick results when applied appropriately to Japanese knotweed.

The reason why this weed killer is highly ranked is because of its ability to be absorbed through the leaves of the Japanese knotweed and trickle down to its roots and ensure that there is total destruction of the entire plant.

Roundup Ultra 300 Professional Weedkiller
Roundup Ultra 300 Professional Weedkiller


This particular weed killer contains 41% glyphosate meaning it is very effective when it comes to the eradication of Japanese knotweed. It acts fast on the weeds; within 7 days one can spot its effects on the weed plant.

This weed killer can also be applied on a relatively big piece of land up to 25,000 square feet. Furthermore, it can get to the roots of any weed plant and affect destruction.

Compare N Save Professional Weed Killer
Compare N Save Professional Weed Killer


Armed with 43% glyphosate, this weed killer swiftly acts on the weed plant and brings to an end any re-growth.

Furthermore, it is rainproof (two hours) thus; one can be rest assured that it will not be washed off by rainwater in case it decides to pour immediately after applying the weed killer.

RM43 contains two herbicides and a surfactant to deliver the permanent removal of Japanese knotweed. Although it is deemed to be more expensive than other similar products, it has exquisite results when it comes to the control and eradication of Japanese knotweed.

RM43 Professional Weed Killer
RM43 Professional Weed Killer


Unlike the above-mentioned Japanese knotweed killer products, Spectracide is mainly a concentrate product meaning before using it one must mix an appropriate formula according to the instructions of the manufacturer.

The upshot of this weed killer for Japanese knotweed is that results will be visible just after a time frame of 3 hours after application. Additionally, planting can take place just after one day has elapsed from the time of its application.

Spectracide Professional Weed Killer
Spectracide Professional Weed Killer

Ortho GroundClear

The weed killer acts fast and its effects are instantaneous. It is capable of getting to the root of the weed plant. This weed killer for Japanese knotweed does not contain glyphosate but it stands out based on its ability to kill weeds and prevent any re-growth.

Ortho Groundclear Professional Weed Killer
Ortho Groundclear Professional Weed Killer


A good Japanese knotweed killer must ensure that it gets to the root and cause complete havoc as fast as possible.

Although it may be hard to make a case for a certain weed killer to be perfect in delivering results against all the other products of a similar nature, one of the things you must consider when selecting such a product is the ability to act excellently on the weed plant.

Eradication of Japanese knotweed is not a walk-in-park hence, the quicker the weed is killed, the better. Finally, considering all weed killers come with instructions manual or rules as to their application, you must always follow these rules without fail if you desire good results.

Want to know more about professional weed killers for Japanese knotweed?

Knotweed Removal aims to provide the most up-to-date information, help and advice for YOU to make informed decisions. If you are unsure or uncertain about how to proceed, please reach out to us and we will gladly come back and advise you as best we can.

Governmental advice can be found here and the UK law covering the removal of Japanese Knotweed as stated under the Wildlife and Countryside Act 1981 can be found here.

The best means to contact us is via our email –

Do not forget we have a library of blogs covering many areas relevant to Japanese Knotweed, our free downloadable How-to Guides and Product Reviews on the latest methods being employed to eradicate or remove Japanese Knotweed.

Knotweed Removal, UK

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