All you need to know about Japanese knotweed

There are a couple of phrases that strike fear into the hearts of property sellers – ‘serious subsidence’ and ‘negative equity’ being two of them. Another phrase you never want to hear is ‘Japanese knotweed’, but is having this invasive plant among your borders really a property death sentence?

Over the course of 2021, it is estimated that £11.8 billion was wiped off the value of UK property due to the presence of Japanese knotweed, with values taking a dip as soon as the plant is identified in a survey report or disclosed by the seller.

This figure, however dramatic it sounds, is a little misleading. Homeowners should be aware that only around 4% of UK properties are affected by Japanese knotweed and even when it is detected, it impacts the value of a property by about 5%. In many cases, a home’s full value is often achieved after an appropriate course of action is taken, despite the plant’s presence.

Even though the plant is found at less than 10% of UK properties, Japanese knotweed isn’t something that can be glossed over when it comes to selling a property. When you have decided to sell, you’ll be asked to fill out a Property Information Form (TA6). 

This form requires sellers to give detailed information about the property and the surrounding area. It is a legal requirement to disclose if the property is or has ever been affected by Japanese knotweed, as its presence can create or worsen cracks in mortar and structural joints, as well as push up through paved and concrete areas. 

It’s important that the ‘affected’ aspect is understood too, as sellers will need to divulge if they’ve ever had to treat the plant if it spread from a neighbouring property. It’s worth noting that a Japanese knotweed plant can be up to 7 metres away from your boundary and still need disclosing on a TA6 form.

Identifying Japanese knotweed (fallopian japonica) can be troublesome if you have no horticultural experience – it can look similar to other harmless plants but the RHS provides a good point of reference. If you’re in any doubt, it’s wise to revert to a specialist removal company for identification.

There is good news. Selling a property is entirely possible if there is Japanese knotweed. It really isn’t the barrier that some people imagine it can be. The vital aspect is to seek guarantee-backed treatment that mortgage lenders will accept. 

It is usually the seller who instructs a specialist Japanese knotweed removal company to excavate and remove the plant’s rhizomes. The plant is rarely eradicated for good through hand weeding or with the use of herbicides as the rhizomes will be buried deep underground. 

If a removal company offers an insurance-backed guarantee, lenders (sometimes referred to as knotweed IBG, a Japanese knotweed indemnity or a knotweed insurance-backed warranty), there’s a high chance a mortgage lender will loan against the property.

Don’t forget, the Japanese variety isn’t the only invasive knotweed out there. Dwarf, giant and bohemian are the other top three knotweeds buyers and sellers need to be on guard for. You can visit the Government’s web page dedicated to the prevention, treatment and disposal of knotweed for further details. 

If you are planning to sell a property where you suspect a case of Japanese knotweed, or are buying a property where the plant has been disclosed on the TA6 form, please contact us for advice and guidance