How to get rid of Japanese knotweed

First: don't make it worse

Before you do anything, know this - Japanese knotweed regrows from a rhizome fragment smaller than a fingernail. So the instinct to cut it, dig at it or pull it up is exactly what helps it spread. Every broken piece is a potential new plant, and the cuttings are legally controlled waste. Don't put it in your green bin or home compost.

Method 1 - Herbicide treatment (the usual choice)

The most common and cost-effective approach is a glyphosate-based herbicide programme applied over several years. Timing matters: the most effective treatment is in late summer to early autumn, when the plant is drawing energy down into the rhizome and carries the herbicide with it.

• How long: typically 3-5 growing seasons to fully exhaust the rhizome.
• Pros: far cheaper than digging; minimal disruption; no soil to remove.
• Cons: slow; the ground stays "contaminated" (with dormant rhizome) during treatment, which can limit building work.

A small garden stand can be tackled with a strong domestic glyphosate weedkiller, but professional-grade products and correct application get results faster and are usually essential for a mortgage-acceptable outcome.

Method 2 - Excavation (dig it out)

For a fast, definitive result - say, before a build or sale - a contractor can excavate the knotweed and its rhizome. The infested soil is either removed to a licensed landfill (expensive) or, on larger sites, buried deep on-site under a root-barrier membrane or screened and treated in a "cell".

• How long: days, not years.
• Pros: immediate; land is usable straight away.
• Cons: much more expensive; heavy machinery; disposal of controlled waste is regulated.

Method 3 - Combined approaches

Many specialists use a hybrid: partial excavation to reduce the bulk, root-barrier membranes to stop encroachment onto a neighbour or a structure, then a follow-up herbicide programme to mop up regrowth. This balances cost, speed and certainty.

What doesn't work

• Cutting or strimming - removes top growth, stimulates the rhizome, and spreads fragments.
• Pulling it up - leaves rhizome behind and breaks it into new plants.
• Burning the canes - doesn't touch the roots.
• Covering it over - knotweed pushes through most membranes and can travel sideways to find light.
• Home composting - spreads it and is an offence if it escapes into the wild.

DIY or professional?

A tiny, isolated stand far from buildings and boundaries can be a patient DIY glyphosate job. But bring in a PCA-accredited specialist if any of these apply: you're selling or mortgaging the property, it's near a structure or a neighbour's land, or the stand is large. Only a professional can issue the insurance-backed guarantee (IBG) that lenders require.

Frequently asked questions

Can you get rid of Japanese knotweed permanently?

Yes - a 3-5 year herbicide programme or a full excavation can clear it for good, provided the underground rhizome is dealt with, not just the visible canes.

What is the cheapest way to remove knotweed?

A herbicide programme is much cheaper than excavation. See our guide to Japanese knotweed removal costs for typical UK prices.

Does cutting Japanese knotweed kill it?

No. Cutting only removes top growth and can spread the plant through fragments. Always treat the rhizome instead.

Written by Alexander White PCA Certificated Japanese Knotweed Surveyor (CSJK) About our surveyors →

This guide is general information, not a treatment plan or professional advice. Herbicides must be used strictly per the label, and knotweed waste is controlled waste under UK law. For a sale, mortgage or legal matter, use a PCA-accredited Japanese knotweed specialist.