Japanese Knotweed and Property — What Buyers Need to Know

What is Japanese Knotweed?

Japanese knotweed (*Fallopia japonica*) is an invasive plant introduced to the UK in the Victorian era. It grows at an extraordinary rate — up to 10 cm per day in summer — and produces a deep, spreading rhizome (root) system that can penetrate foundations, drains, and walls. It is notoriously difficult to eradicate and expensive to treat.

It is a criminal offence to plant Japanese knotweed or cause it to spread to neighbouring land under the Wildlife and Countryside Act 1981.

How to Identify Japanese Knotweed

• **Stems:** hollow, bamboo-like stems with purple speckles, forming dense clumps up to 3 metres tall by late summer
• **Leaves:** distinctive shield or heart shape with a flat base, bright green, up to 14 cm long
• **Flowers:** small, creamy-white flowers appearing in late summer (August–September)
• **Winter:** dies back to leave brown, hollow canes that persist through winter; new growth emerges from ground level in spring

If in doubt, instruct a specialist surveyor — do not rely on your own identification.

Mortgage Implications

Many mortgage lenders will refuse to lend on a property where Japanese knotweed is present within **7 metres of a habitable space** unless a professional treatment plan with an **insurance-backed guarantee (IBG)** is in place from a recognised contractor (typically a member of the Property Care Association).

Some lenders apply a category system (RICS categories A–D) to assess risk. Category A (knotweed within 7 metres of habitable space and causing damage) is the most serious and can make a property unmortgageable until treated.

Treatment Options and Costs

Chemical treatment is the most common approach. The rhizome must be killed, not just the visible stems — which is why treatment programmes span multiple growing seasons.

What to Check in the TA6 Form

The **TA6 Property Information Form** completed by the seller includes a direct question about Japanese knotweed. Sellers must declare:

• Whether Japanese knotweed is present or has previously been present on the property
• Whether a treatment plan and IBG is in place

Misrepresenting this can constitute a **misrepresentation** under the Misrepresentation Act 1967, potentially giving the buyer grounds for rescission or damages after completion.

What to Do if Knotweed Is Found During a Survey

1. **Commission a specialist survey** from a Property Care Association (PCA) member

2. **Confirm lender requirements** — check with your mortgage lender whether they require specific treatment before they will lend

3. **Negotiate a price reduction** to cover the cost of treatment, or require the seller to obtain an IBG treatment plan before exchange

4. **Do not exchange** until a treatment plan with an IBG is in place if your lender requires it

Knotweed does not automatically mean you should walk away from a purchase — but it must be managed properly and documented. Property Passport UK stores property documents including knotweed treatment plans and IBGs, ensuring this critical information is accessible to future buyers and lenders.