Is Japanese knotweed in my garden? What clearance firms won't touch

If you have Japanese knotweed, an ordinary garden clearance crew should stop work in that part of the garden and tell you. Not because of a rule they invented, but because strimming, chipping, digging or carting away knotweed spreads it, and spreading it can be a criminal offence. Knotweed waste is controlled waste that has to go to a licensed site, which a green waste round cannot do. Having knotweed is not illegal and it does not have to be removed, but it needs a specialist rather than a mower.

This guide is general information, not legal advice.

How to identify it, season by season

Japanese knotweed (Reynoutria japonica, still often listed as Fallopia japonica) is unmistakable once you know it and easy to confuse before that. The RHS profile describes it through the year:

• Early spring. Rounded pink or red buds push up at ground level in a distinct clump and open into reddish-purple shoots. Growth is fast: asparagus-like spears appear where there was bare soil a fortnight earlier.
• Late spring and summer. Stems reach around two metres: hollow, bamboo-like, green with reddish-purple speckling, with clear nodes and a zigzag pattern. Leaves are roughly shovel shaped with a flat base, held alternately, one at each node.
• Late summer into autumn. Sprays of small creamy-white flowers appear.
• Winter. Top growth dies back to dry, brittle brown canes that stay standing or collapse into a tangle, one of the easiest signs.
• Underground, all year. Thick woody rhizomes run a metre or more down and sideways. Snap a fresh piece and the inside is vivid orange or yellow under a dark brown skin.

Common lookalikes

Most suspected knotweed turns out to be something else. The usual confusions:

• Bindweed. Twines around other plants, with white trumpet flowers and arrow-shaped leaves. No upright cane, no nodes.
• Bamboo. Woody ridged canes that persist through winter and long narrow leaves. Knotweed canes are hollow, die back each year and carry broad leaves.
• Dogwood. Red winter stems, but opposite leaves and solid stems.
• Himalayan honeysuckle (Leycesteria formosa). Hollow green canes very close to knotweed, but with opposite leaves and drooping claret flower bracts.
• Russian vine (Fallopia baldschuanica). A genuine relative, but a rampant climber rather than a clump of upright canes, as are the persicarias and ornamental knotweeds common in older borders.

A useful test: Japanese knotweed has alternate leaves, hollow zigzag stems and orange rhizomes. Opposite leaves or solid stems mean it is not knotweed. If you are unsure, photograph the shoot, a stem node, a leaf and the base of the clump, and have a specialist confirm it before anyone cuts anything.

What the law says

• Having it is not an offence. GOV.UK is explicit that you do not legally have to remove Japanese knotweed from your land unless it is causing a nuisance, but you can be prosecuted for causing it to spread into the wild (prevent Japanese knotweed from spreading).
• Spreading it can be. Japanese knotweed is listed in Schedule 9 to the Wildlife and Countryside Act 1981, and under section 14 it is an offence to plant or otherwise cause it to grow in the wild.
• It is controlled waste. Knotweed material, and soil contaminated with it, is controlled waste under the Environmental Protection Act 1990. It must be moved by a registered waste carrier to a site permitted to accept it, usually a licensed landfill. It cannot be composted, put in a green bin or taken to a household recycling centre.
• You must stop it leaving your property. Letting it grow through a fence into a neighbour's garden can lead to a private nuisance claim.

Why a clearance crew has to stop

Knotweed spreads in the UK almost entirely by fragments rather than seed, and a very small piece of rhizome can grow into a new plant. Normal clearance methods are almost perfectly designed to break it up and move it about:

• Strimming flings fragments across the garden and into neighbouring ground.
• Chipping contaminates the machine, and then the next three gardens it visits.
• Digging or rotavating breaks the rhizome into dozens of viable pieces and mixes them through the topsoil.
• Loading it into a van with ordinary green waste contaminates the whole load, and the tipping site will not take it.
• Moving soil to another part of the garden simply plants it somewhere new.

There is also the paperwork: a clearance firm's waste carrier registration lets it move garden waste, not dispose of controlled waste at an unsuitable site. A crew that carries on regardless puts your liability and theirs on the line.

Selling, buying and mortgages

Knotweed matters most when a property changes hands.

• The Law Society's TA6 property information form asks the seller directly about Japanese knotweed. Answering it wrongly can lead to a misrepresentation claim after completion.
• RICS published a professional standard on Japanese knotweed and residential property in 2022, setting out management categories A to D for valuers and a framework for when a lender needs a retention or a treatment plan. It also notes that knotweed is less likely to cause significant structural damage than commonly assumed.
• Lenders commonly want evidence of a professional treatment programme with a long-term insurance-backed guarantee.

None of that makes a sale impossible. It means dealing with it early is much cheaper than dealing with it mid-conveyance.

What specialist treatment involves

Two broad routes, and the right one depends on the site and your timescale:

• Herbicide programme. Repeated glyphosate treatment, usually applied in late summer as the plant draws nutrient down to the rhizome. The RHS notes that chemical control takes at least three growing seasons, and plans are typically written over three to five years with monitoring visits.
• Excavation. Digging out the rhizome and either removing it to a licensed landfill, burying it on site under a membrane, or screening the soil. Faster, the usual answer where building work is planned, and far more expensive.

GOV.UK advises using a specialist rather than treating it yourself, and points to contractors with BASIS or Amenity Forum accreditation, or membership of INNSA or the Property Care Association. An accredited firm can confirm identification, produce a management plan and provide the insurance-backed guarantee lenders look for.

What we do when the knotweed box is ticked

Our quote form asks whether there is anything in the garden that is not garden waste, with a checkbox for Japanese knotweed. Tick it and the enquiry is flagged: we do not send a clearance crew to strim it and we give no online price for the affected area, because any hazard flag goes to a free survey rather than an instant estimate. Where the rest of the garden can be worked on safely, with the knotweed fenced off and tools cleaned before the crew leaves, we pass that part of the job to one local specialist as usual.

For the rest of the garden, see overgrown garden clearance, bramble clearance and green waste removal, with prices in the garden clearance cost guide.