Japanese knotweed removal is vital as it can cause significant and long-term damage to gardens, buildings and infrastructure.
Its underground rhizome system spreads widely beneath the surface and can exploit weaknesses in concrete, drains and masonry.
Because the plant can regenerate from even tiny fragments and remain dormant for many years, partial treatment options often lead to regrowth.
Experts stress that if you identify Japanese knotweed in your garden, only complete removal of the plant and its entire root system can permanently solve the problem.
The only true method for removing Japanese knotweed
Emily Grant, Director at invasive plant specialist Environet, is clear that Japanese knotweed can only be properly removed through full excavation.
She says: “A more belt-and-braces approach is excavation, where all the knotweed plant material above and below the ground is entirely removed.”
She explains that successful removal depends on eliminating both the visible plant and the extensive underground rhizome system that drives regrowth. This requires removing all contaminated soil from the site and processing it carefully to ensure no fragments remain.
Excavation is the only method that achieves full eradication because it physically removes the entire plant system.
Grant explains that Japanese knotweed cannot be controlled reliably at the surface level alone, as its rhizomes can extend deep underground and spread laterally. Even the smallest fragment left behind can regenerate into a new plant.
Emily Grant is a Director at Environet, a UK company specialising in invasive plant management and Japanese knotweed removal. She has been part of the senior leadership team since 2020, helping to oversee operations and deliver specialist removal.
Can herbicides kill Japanese knotweed?
Herbicide does not remove or kill Japanese knotweed and should not be considered a permanent removal method.
Grant explains: “Herbicide is the least expensive option, costing around £3,500, but the chemicals can induce the plant into dormancy rather than kill it completely, so we always advise customers to only consider it as a control method.”
She adds that even when no growth is visible for long periods, the underground rhizome system can remain alive and reactivate if the ground is disturbed. For this reason, herbicides cannot deliver permanent removal.
However, herbicides can be useful for containing the issue until a more final solution is found.
Best herbicide to contain Japanese knotweed
Designed to tackle tough garden weeds quickly and effectively, Westland Resolva Xtra Fast Weedkiller is one of the better herbicide options for helping to contain Japanese knotweed growth above ground.
Can you remove Japanese knotweed yourself?
Experts strongly advise against DIY attempts due to the plant’s ability to regenerate from extremely small fragments.
Nic Seal, who founded Environet, states: “Beware of DIY solutions or trying to eradicate the weed yourself. Cutting it down repeatedly, pouring diesel on it, covering it in salt, burning it, burying it and saturating it in over-the-counter weed killers are the most common methods I come across, but they categorically don’t work.”
He also warns that improper handling can also spread contamination if soil or plant material is moved incorrectly.
Nic Seal is the founder of Environet, which he established in 1996 after a background in environmental science and engineering. He grew the business into one of the UK’s leading invasive plant specialists, known particularly for Japanese knotweed identification and removal solutions.
How much will it cost to call in a professional?
The cost of professional removal depends on the size and depth of the infestation, as well as site conditions.
Emily Grant explains: “Knotweed can regrow from a piece of rhizome as small as a fingernail, so the soil is carefully sifted to ensure every tiny fragment is removed. Excavation costs depend on the size of the infestation, but usually start at around £7,000.”
Although more expensive than temporary control methods, excavation is the only approach that guarantees full removal of the plant and its underground system.
Can Japanese knotweed be eradicated completely or will it come back?
Japanese knotweed can be fully eradicated only when the entire rhizome system is removed from the ground.
Emily Grant explains that incomplete treatment is the main reason infestations return. The plant’s underground system can remain dormant for many years and reactivate when disturbed.
Because excavation removes both the visible plant and the rhizome network, it eliminates the conditions that allow regrowth.
Nic Seal also warns: “Japanese knotweed can lie dormant for up to 20 years only to strike again when you least expect it.”
Japanese knotweed removal requires a complete and definitive approach rather than partial treatment or suppression.
Experts are clear that excavation is the only method that achieves true eradication, as it removes both the plant and its underground system.
Given its ability to regenerate from tiny fragments and remain dormant for decades, proper professional removal is essential to ensure the infestation does not return once it has been dealt with.
