Japanese Knotweed? What to do before selling your home

The threat posed by Japanese Knotweed to your property is often exaggerated. The risk that you may not be ultimately able to sell your home is not.

See also: What to check before buying a home with Japanese knotweed

Japanese knotweed

If you are aware of or have reason to believe there is knotweed in the vicinity of your property, the following steps could be the difference between a successful sale and your home suffering a significantly diminished value.

The dreaded TA6 'Knotweed Question'

If you are surprised by the 'Knotweed Question' on the 'Seller's Property Information Form (TA6)' - you may have left it too late

Once you have accepted an offer on your property, the buyer's conveyancing solicitor will carry out due diligence on behalf of the buyer.

The seller will complete a number of forms relating to the property and these will be forwarded to the buyer. One of these forms is the Seller's Property Information Form (TA6) which covers a broad range of things relating to the property such as subsidence or any historical and ongoing disputes with neighbours.

Since 2013 the form has included the following question:

"Is the property affected by Japanese Knotweed? Yes, No or Don't know.

If Yes, please state whether there is a Japanese Knotweed management plan in place and supply a copy."

Approved knotweed management plan

If an approved management plan is not already in place it may be (practically) too late to start one - at least within the typical time frame afforded by an impatient buyer. It can take weeks or even months to get the program underway and most buyers will not be prepared to wait around for this.

Even if the buyer is prepared to wait they will still face uncertainty as to whether their lender will be prepared to lend and will likely keep looking for another property in the interim.

Furthermore, if there is a chain it will be more likely to collapse during the delay.

Even if the buyer is prepared to wait they will still face uncertainty as to whether their lender will be prepared to lend and will likely keep looking for another property in the interim.

Lying on this form can have very serious consequences

The TA6 form is part of the contract of sale. If you tick the wrong box (or lie) on this form and the buyer suffers any consequent loss, then the buyer will be able to sue you for misrepresentation. Such a claim would not only cover the buyer's survey and legal costs but also any diminution of value of the property.

As the property will be harder to mortgage, the consequent loss of value can run into hundreds of thousands.

What can you do before putting your property on the market?

Now that we have established (hopefully) that it is a bad idea to lie about Knotweed, there are a number of steps you can take to avoid any post-offer hassle that might otherwise lead to an aborted sale.

There is no legal requirement for you to do anything

The responsibility of managing Japanese Knotweed lies with the owner or occupier of the site where knotweed is present. At present, there is no statutory requirement to eradicate, destroy or report the presence of this non-native species as Japanese knotweed is not currently listed under The Weeds Act 1959.


Japanese Knotweed is a highly invasive plant.

Ignoring the plant will only make matters worse. In order to prevent the rapid spread of this invasive plant, it is highly recommended to take prompt action to control it. In most cases, the actual plant poses less of a threat than the potential overreaction of the buyer's mortgage lender.

Most lenders simply won't lend on a property affected by Knotweed unless certain criteria are met. Lender's positions on this vary and they are constantly revising their lending criteria.

For up to information on how lenders consider Knotweed see the Council of Mortgage Lenders Handbook. At the time of writing the HSBC, the UK's largest lender requires any property with Knotweed within the boundary or on neighbouring land within 7 metres of the habitable space to have:

  • A fully paid up treatment plan which has commenced with an appropriately qualified person or company such as an accredited member of an industry recognised trade association such as the Property Care Association and the Invasive Non-Native Specialists Association
  • A minimum 10-year insurance backed guarantee can be provided on completion of the works.

The authors personal experience with the HSBC

In 2015 I sold my first floor flat in North London. The garden flat below had what can only be described as a sprig of knotweed some 8 metres from the property footings.

The plant had been there for an estimated 50 years and had not spread. It was chance glance over the fence by a neighbour in 2013 that alerted me to the plant's existence. I arranged an immediate survey which confirmed the plant was knotweed.

Thereafter I signed up to a £1,500 eradication program which promised to:

  • Identify any Japanese knotweed at the site/property
  • Assess the scale of the infestation & the properties affected
  • Assess the risk posed to the property/site by any Japanese knotweed
  • Make professional recommendations and offer remedial treatment advice

I then instructed the firm to carry out the treatment plan. The first spray killed the plant and it never returned.

Subsequent revisits confirmed no regrowth and 2.5 years into the 3-year plan I put the property on the market. Despite this immediate treatment success, some 3 years later I almost lost the sale of my flat as the buyer's lender (HSBC) seemed unwilling to lend on it. This would have scuppered the sale and resulted in a catastrophic loss of value in my home.

Passed from pillar to post

The mortgage application was passed around internally as the bank had not designed its processes to efficiently deal with the matter. Solicitors chased constantly but couldn't get a straight answer from the bank.

In the end, I contacted the lender myself and the key issue was an ambiguous word in the small print of the insurance policy. Ultimately I worked with the knotweed company to find an alternative suitable policy from another insurer. This process took months to arrange.

£1,500 may seem like a lot to spend on a quick spray of weedkiller - and it is. However, to attempt treatment yourself or to delay the instruction of an approved treatment company would be to miss the point entirely.

What matters is the indemnity policy

What matters is the issue of the indemnity policy upon completion of the treatment program. Without this policy, the lender cannot offset the risk and will not see the property as suitable security for the mortgage.

Thankfully I had a program in place and nearing completion at the point of the sale. Nevertheless, the mere mention of the word Knotweed sent the HSBC into a spin and protracted the sale process by some 3 additional months.

During this time the buyer constantly threatened to pull out and we had no certainty that the HSBC would issue the mortgage offer.

Key steps if you discover knotweed at or near your home:


  • Speak to your neighbours immediately. If the plant has spread to or from their land then any treatment you carry out solely on your property will be a waste of time as the plant must be killed in its entirety. Your neighbour will likely be happy to share the cost of the treatment.
  • Get a PCA Certified company to carry out an immediate inspection to confirm that the plant is in fact Knotweed.
  • Ask for a treatment plan proposal from 2 or 3 companies - costs vary considerably.
  • Make sure that a suitable 10 year insurance backed guarantee and indemnity policy will be issued upon completion of the plan. It is critical that this policy is accepted by all major UK lenders, if it isn't speak to another company.
  • If you are about to go on the market be prepared to pay for the treatment, in its entirety, up front. Often the lender insists that the plan is paid for up front as the subsequent owner may not pay for the treatment once they move in and the lenders security will be compromised.


  • Ignore it - the problem won't go away
  • Attempt to remove it yourself. Knotweed is a notifiable plant and disposing of it through non-formal procedures can incur a fine of up to £2,500 and even earn you an ASBO!
  • Don't cut it, trim it or prune it in any way and don't disturb the soil around or anywhere near the plant.
  • Don't cut the grass or any other vegetation near the plant.
  • Don't spray it with weed killer yourself. There is more to killing it that simply spraying Roundup. A professional will know the best application method, timing, treatment intervals etc.

Take control

Taking control of the situation is paramount. The above advice should put you well ahead of the curve when it comes to sell your home and hopefully avert any lender issues that might otherwise stop your sale going through.