Ben Lindley, Company Director at Japanese Knotweed Ltd. Last reviewed on 9th November 2026.
Japanese knotweed – to Control or to remove?
That is the question – and it’s one that we get asked by most clients. And when it comes to Japanese knotweed doing nothing simply isn’t an option!
When it comes to knotweed removal – Herbicide vs Excavation, which is better and why? In this article we explore the benefits of control via a herbicide management plan versus complete removal via excavation to answer the question; is getting knotweed removal over and done with the better option?
CONTROL
To get knotweed under control and safeguard property or land, a treatment plan (often referred to as a Knotweed Management Plan or KMP) involves a series of planned herbicide applications typically carried out over a period of 3, 5 or 10 years.
Herbicide treatment of Japanese knotweed works by entering the plant’s system via its leaves (by spraying or wiping) or its stems (by injecting the stems with herbicide). The idea of herbicide treatment is not to kill off the foliage, as the plant can survive via its underground rhizome network, but to ensure the herbicide travels down into the rhizomes, which over time reduces the viable rhizomes and puts the plant into a dormant state. With each year of treatment, the rhizome system gets less efficient at growing new plants, hence controlling the growth. The best time to treat Japanese knotweed is between flowering (August) and when the plant starts to drop its leaves for winter (October-November). This is when the plant is actively drawing nutrients down into the rhizome network in preparation for its dormant period over winter and will carry the herbicide with it.
It’s important to note that in most situations, but particularly with mature knotweed stands that possess visible crown material, herbicide control alone is unlikely to completely render the plant unviable. Often it remains in a dormant state for many years, and can appear to be eradicated, but the rhizomes remain viable and can regrow new plants if they are disturbed.
BENEFITS:
- Less invasive than excavation.
- The 2-3 treatments can be easily factored in to planned works on residential properties or commercial sites.
- Often a good option for sites that are not deemed for any development activity, as the ground can remain intact and with minimal disturbance to the habitat.
- Can be cheaper.
REMOVAL
Dense or deep rhizome may remain viable while being locked in a herbicide induced dormancy. Disturbance of the treated knotweed area even after successful completion of herbicide treatments can therefore result in re-growth. If the area of ground where the knotweed resides is likely to be disturbed, excavation will be recommended for complete eradication of knotweed. We will discuss the best method of excavation to use, based on the extent of infestation, the site and its intended use, and any other considerations such as access.
BENEFITS:
- On completion, when the knotweed has been fully removed, excavation allows for unimpeded development of the area.
- Peace of mind. Whilst herbicide manages regrowth, excavation gets rid of the problem for good, making ground fit for future development.
- Guarantee for future purchasers of land of property, that the site is knotweed-free.
- A one-off cost can often be factored into a project’s budget more easily. Especially if you need to use up any end of financial year budget rather than losing it.
CONCLUSION
If you’re happy to knotweed controlled over a longer period then opt for a herbicide management plan. If you need knotweed gone now – excavation is a one
Have a question? Why not speak to our team to see how we can help.