Does herbicide kill Japanese knotweed?

... and how treatment plans work



May 11, 2021

Feared by homeowners and developers alike, Japanese knotweed can devastate our gardens, homes, offices and building sites, costing thousands of pounds to remove. Worse still, it can delay development projects and devalue residential properties by up to 20%.

However, there is hope for those affected by Japanese knotweed in the form of herbicide treatments.

Spraying Japanese knotweed, herbicide treatment

What are herbicide treatments?

Herbicide treatments are usually applied by Japanese knotweed removal companies who use a high-grade glyphosate-based solution to stop the plant spreading.  Typically, glyphosate is sprayed onto the leaves and stems of Japanese knotweed, which then absorbs the toxic liquid and transports it via its root system. Finally, the herbicide reaches the rhizome (or, root) rendering it dormant. So unless the rhizome is disturbed, the Japanese knotweed is unlikely to grow back above ground after treatment.

Will glyphosate kill Japanese knotweed? 

No, herbicides (including high-grade glyphosates) will NOT kill Japanese knotweed. This is misunderstood by many in the knotweed removal industry. In fact, The University of Swansea conducted tests on Japanese knotweed in 2016 and proved that herbicide treatment simply won't kill the plant.

However, that’s not to say herbicide treatments are not effective. Using glyphosate is still the most common removal treatment plan used by experts, including our team at TCM!

Although herbicides don’t kill Japanese knotweed, glyphosate exhaust the plant’s energy, essentially leaving it lifeless. But it might make you wonder if such treatments are worth it?

Herbicide treatments or excavation

There are pros and cons to using herbicide treatments and seeking excavation. Often, your best treatment plan is determined by the location of the knotweed, whether you’re a homeowner or developer, and ecological factors.

Here's a breakdown:

Why choose herbicide treatments?

  • Herbicide treatments are often favoured by residential property owners since it is a more affordable method of removing Japanese knotweed. 
  • Herbicides are less invasive - and experienced knotweed removal team will spray the growth area a few times over several summers.  Although the process is long, homeowners will hardly notice the work being done and will still be able to enjoy and use their garden.   
  • Glyphosates can also be injected into Japanese knotweed.  The means that surrounding wildlife, and the rest of your garden, is safe! 

Why choose excavation?

  • Land and building developers tend to excavate Japanese knotweed from their site.  It is significantly more costly but the job is completed quickly, which is essential when you are working to building stage phases.
  • Once experts excavate the knotweed, developers and builders are able to use the land immediately, without restriction.  The same cannot be said for herbicide treatment plans - here the residents are asked to carefully use the area where the rhizome lies. 

When to hire invasive weed experts

Across the UK, homeowners and developers are starting to realise that removing Japanese knotweed is a real challenge.  Whether or not your infestation requires herbicide treatments or excavation, it is always advised to discuss your options with a Japanese knotweed specialist.

If you have found Japanese knotweed in your garden, on your land, inside your home or other buildings, have it checked out immediately by someone who has a good understanding of invasive plants and their destructive nature.  The longer you leave it, the further the plant will grow, taking over natural habitat, and causing untold damage to walls, paths, and buildings.  

Get in touch today to find out more about how we can help with your knotweed or other invasive weed infestation.