A map has revealed the areas in south east London with the highest numbers of Japanese Knotweed sightings, and parts of Norwood and Bromley are amongst the highest.

Japanese Knotweed is an invasive non-native plant that can grow up to 7ft tall and root itself deep in the ground, which can affect the foundations of your home and make it difficult to sell.

According to the Property Care Association (PCA), Japanese Knotweed is becoming a “more viable” plant, with advice to homeowners to treat it to avoid implications on property structures.

Where is it most prevalent in south east London?

A Heatmap created by Environet UK, comprising of over 51,000 sightings of Japanese Knotweed in the UK and Europe, has revealed the south east London areas where the plant has been sighted.

According to Environet UK, the Heatmap is based upon reported sightings, where some are verified, and some are not.

As Japanese Knotweed is underground during the winter months, it is also possible that some sightings have gone undetected.

Number of reported knotweed occurrences in south east London: 

According to findings, the highest number of reported sightings was within a 4km distance of West Norwood Station with 353 followed by the area within a 4km radius of Gipsy Hill Station with 312.

Other areas included the area around the Horniman Museum in Lewisham with 305 and Crystal Palace Park in Bromley with 273 sightings of Japanese Knotweed.

Areas with lower figures of Japanese Knotweed sightings in south east London were within a 4km radius of New Cross Gate with 215 and the 4km surrounding Lewisham Hospital with 213.

Credit: Environet UK

Here are the top ten areas with the highest numbers for Japanese Knotweed sightings:

  • 353 within 4km of West Norwood Station, SE27 0HU
  • 312 within 4km of Gipsy Hill Station, SE19 1PL
  • 305 within 4km of Horniman Museum, SE23 3PQ
  • 273 within 4km of Crystal Palace Park, SE19 2GA
  • 257 within 4km of King's College Hospital, SE5 9RS
  • 255 within 4km of Sydenham Station, SE26 5EU
  • 244 within 4km of Brockley Station, SE4 2RW
  • 239 within 4km of Catford Station, SE6 4RW
  • 215 within 4km of New Cross Gate Station, SE14 6AR
  • 213 within 4km of University Hospital Lewisham, SE13 6LH

How to spot it

Japanese Knotweed can be identified by its distinctive red stems in February, when it emerges with fleshy shoots and pinkish buds.

During the summer months these shoots grow rapidly into tall bamboo-like canes that can grow up to 7 ft tall with purple flecks.

According to the Royal Horticultural Society (RHS) the plant can also be distinguished by heart or shovel shaped leaves that grow up to 14cm in length.

Why is it a problem for property owners?

The issue posed by Japanese Knotweed is that it is particularly difficult to remove by hand or using domestic weed killers.

To remove Japanese Knotweed effectively, stronger specialist chemicals are needed, or specialist contractors.

Under the Wildlife and Countryside Act (1981) it is an offence to cause Japanese Knotweed to grow in the wild and anyone fly-tipping the perennial shrub can be prosecuted.

Homeowners looking to sell their properties are required to state if Japanese Knotweed is present on their property, through what is known as a TA6 form.

According to Daniel Docking, the PCA’s Invasive Weed Control Group technical manager, the current climate conditions could have a detrimental impact on native plant species.

Daniel said: “We can still expect late season frosts and dry weather in March and April, but Japanese knotweed has already started to establish itself and the resilience of the plant will mean it is in a strong position to thrive.

“As Japanese knotweed becomes more visible, we encourage anyone with concerns about the plant to seek expert help.

“Advice sought quickly will help to control and manage the situation effectively.

“Japanese knotweed is tied to legislation, which means landowners have a responsibility to manage infestations responsibly.

“Our ICWG members have a range of options to treat infestations, so it’s essential to engage a competent Certificated Surveyors in Japanese knotweed (CSJK) who will have the specialist skills and knowledge to identify Japanese knotweed or any other invasive plants that may be present.”