Japanese knotweed: 10 Sheffield high-risk areas revealed, how to stop it from spreading

Japanese knotweed, an invasive plant that could destroy your property, has been found to be infesting a number of Sheffield areas, latest figures have revealed. According to a heatmap provided by invasive plant specialists at Environetuk, over 224 infestations have been found within a 4km radius across the city.

Due to its rapid growth rate of up to 10cm per day, Japanese knotweed has been known to cause damage to building structures and substructures by targeting and attempting to grow through weak places, such as fractures in masonry. It can also grow up to three metres tall in spring and summer and its roots can reach down to 20 metres underground.

Homeowners have also been wary of how destructive the plant can be. In London, a man has successfully sued the previous owner of his house after discovering a large amount of Japanese knotweed in his garden, resulting in a £200,000 court bill.

Making a seller aware of the presence of Japanese knotweed has been a legal requirement since 2013. According to the Royal Horticultural Society, the seller is required to state whether Japanese knotweed is present on their property through a TA6 form - the property information form used for conveyancing.

In addition to destroying pipes and drains, its destructiveness could weaken paving or building foundations, resulting in foundational collapse and inadequate flood defences. Japanese knotweed is cited as a property defect by RICS Homebuyer Reports, which has the potential to lower the value of a property by 5% to 15%, according to surveyor specialists at Stokemont.

10 Sheffield areas with Japanese knotweed infestations

According to Environetuk, these are the Sheffield areas with the most Japanese knotweed infestations within a 4km radius. You can check if your area is infested with the destructive plant by keying in your postcode.

1. Tinsley - 168 reported occurrences
2. Hillsborough - 140 reported occurrences 
3. Meersbrook - 135 reported occurrences
4. Darnall - 132 reported occurrences
5. Worrall - 89 reported occurrences 
6. Oughtibridge - 79 reported occurrences
7. Handsworth - 75 reported occurrences
8. Fulwood - 70 reported occurrences
9. Stannington - 69 reported occurrences
10. Ecclesfield - 45 reported occurrences

How to stop knotweed spreading 

According to the Government website, one should not treat knotweed on their own unless they have the appropriate skills and experience, or they can find companies that specialise in treating knotweed.

Spraying or injecting the stems with chemicals can be an effective treatment to stop knotweeds spreading but only approved herbicides can be used. Respraying is also needed as it usually takes at least three years to treat Japanese knotweed.

When using chemicals, you may need to:

• make sure anyone spraying holds a certificate of competence for herbicide use or works under direct supervision of a certificate holder
• carry out a Control of Substances Hazardous to Health assessment
• get permission from Natural England if the area is protected, for example sites of special scientific interest
• get permission from the Environment Agency if the plants are near water