Digging a conservatory base disturbs the ground, and disturbed knotweed rhizome can regrow. This guide sets out what GOV.UK guidance for England says about Japanese knotweed on land and in soil, and how section 14 of the Wildlife and Countryside Act 1981 applies in England and Wales. Scotland and Northern Ireland have separate guidance and, for Scotland, a differently worded section 14. This is general information, not legal or technical advice.

Where the law stands on a garden with knotweed

The Environment Agency, Defra and Natural England guidance for England says a landowner does not legally have to remove Japanese knotweed from their land unless it is causing a nuisance, but they must stop it spreading off the property and can be prosecuted for causing it to spread into the wild. The same guidance notes that soil or plant material contaminated with non-native invasive plants can cause ecological damage and may be classified as controlled waste.

The offence sits in section 14 of the Wildlife and Countryside Act 1981. In England and Wales, section 14(2) makes it an offence for a person to plant, or otherwise cause to grow in the wild, any plant included in Part II of Schedule 9 to the Act. Section 14(3) provides a defence for a person who took all reasonable steps and exercised all due diligence to avoid committing the offence. The Scottish version of section 14 is worded differently, and refers to plants grown in the wild outside their native range.

Why a conservatory project raises the stakes

The GOV.UK guidance explains that knotweed spreads by direct rhizome (root) growth and by new growth from stem and rhizome fragments, and that a new plant can grow from a piece of rhizome as small as 1cm. It also says the rhizome can remain dormant in the soil for many years and will regrow if disturbed or if the soil is relocated. Excavating for footings, drains or a service trench is therefore the kind of activity that can move fragments around a site or off it.

The guidance identifies man-made habitats such as roadsides, waste ground and railway embankments as places where knotweed commonly grows, and it is also found along rivers and streams. It does not say gardens are exempt, so a plot with a stand of knotweed near the planned footprint is a matter to raise before groundwork starts.

Treatment and disposal options on site

The guidance advises against treating knotweed without the appropriate skills and experience, and points to specialist companies. Chemical treatment by spraying or injecting stems can be effective, but only approved herbicides may be used, repeat applications are needed, and it usually takes at least 3 years to treat Japanese knotweed. Depending on the location, a certificate of competence, a Control of Substances Hazardous to Health assessment, Natural England permission for protected areas or Environment Agency agreement near water may be required.

Where knotweed is buried, the Environment Agency must be notified at least one month beforehand. The material must be buried on the site it came from, at a depth of at least 5 metres if no geotextile membrane is used, or at least 2 metres if the material is sealed in a membrane. A membrane must be undamaged, securely sealed, ultraviolet resistant and expected to remain intact for 50 years. Dead brown canes can be composted on site if they are cut, not pulled, at least 10cm above the crown.

For burning, the guidance warns that crowns and rhizomes may survive, so burnt material still needs burial or off-site disposal.

Taking soil away from the site

Where the material cannot be dealt with on site, the guidance says it must go to a landfill site or incineration facility with the correct type of permit, using a registered waste carrier, and the Environment Agency must be told where it was sent. Knotweed waste must not be disposed of with other surplus soil, soil contaminated with knotweed must not be sold as topsoil, and contaminated soil can be reused only after treatment on the site where it grew. A waste licensing exemption cannot be obtained for the use of Japanese knotweed.

These are rules for the person managing the waste, so when a conservatory installer is removing spoil, a homeowner can ask who is responsible and whether they use a registered carrier.

What to ask the installer

Before groundwork, a homeowner can confirm whether the survey looked at the wider garden, whether the installer has a plan for any suspected knotweed, and who will pay for specialist treatment. The wider survey and contract questions are in the guide to choosing a conservatory installer, and ground questions are in the guide to conservatory foundations. The GOV.UK guidance lists accreditations to look for in a specialist contractor: Amenity Forum membership and BASIS registers. It also notes that many such companies belong to the Invasive Non-Native Specialists Association or the Property Care Association.

FAQs

Do I have to remove knotweed before building a conservatory?

The England guidance says there is no legal duty to remove Japanese knotweed from your land unless it is causing a nuisance, but it must not spread off the property or into the wild.

Can I dig the soil out and put it in a skip?

The guidance says knotweed waste must not be disposed of with other surplus soil, and it must go to a permitted site through a registered waste carrier.

Does this apply in Wales or Scotland?

The GOV.UK page applies to England and links separate guidance for Scotland, Wales and Northern Ireland. Section 14 is worded differently in Scotland.

The bottom line

In England, Japanese knotweed in a garden does not have to be removed, but it must not spread, and soil contaminated with it can be controlled waste. Digging foundations near a stand of knotweed is the moment to bring in a specialist and plan disposal in advance. Section 14 of the Wildlife and Countryside Act 1981 makes causing a listed plant to grow in the wild an offence in England and Wales, subject to a due-diligence defence.

Sources

This guide draws on the following sources, current as of 25 September 2026:

• Environment Agency, Defra and Natural England, “How to stop Japanese knotweed from spreading” (GOV.UK, last updated 12 February 2026)
• legislation.gov.uk, “Wildlife and Countryside Act 1981, section 14: Introduction of new species etc.”

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Compare Conservatories is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not legal or planning advice on any specific property — always confirm requirements directly with your local planning authority.