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Kent's hotspots for Japanese Knotweed revealed


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Tunbridge Wells, Tonbridge and Canterbury have been named the top three hotspots for Japanese knotweed in Kent.

The plant is one of the UK's most invasive species which, if left untreated, can damage buildings by targeting cracks and growing through them.

A map showing hotspots in Kent. Picture: Environet UK
A map showing hotspots in Kent. Picture: Environet UK

As the growing season gets underway, invasive plant specialist Environet UK revealed the knotweed hotspots for spring 2022 in Kent using data from its interactive online tracker.

Tunbridge Wells came out on top with 47 infestations a within 4km radius.

Neighbouring Tonbridge was second with 33, and Canterbury came third with 30.

Following closely behind was Hythe with 22, and Folkestone and Maidstone are also hotspots both with 20 infestations within 4km radius.

Japanese knotweed first arrived in the UK in 1850 in a box of plant specimens delivered to Kew Gardens.

It's one of the UK's most invasive species. Picture: Environet UK
It's one of the UK's most invasive species. Picture: Environet UK

Favoured for its rapid growth and heart-shaped leaves, it was quickly adopted by gardeners and horticulturalists who were oblivious to its invasive nature.

Knotweed hibernates over winter but in March or April it begins to grow, with red or purple spear-like shoots emerging from the ground which quickly grow into lush green shrubs with pink-flecked stems and bamboo-like canes.

However the plant can cause serious problems if left unchecked, with the potential to grow up through cracks in concrete, tarmac driveways, pathways, drains and cavity walls.

The roots can grow as deep as three metres and spread up to seven metres horizontally.

While serious damage to property is rare because of regulations, it commonly impacts use of the garden, causes legal disputes between neighbours and can impact a property’s value by around 5%.

Specially trained sniffer dogs can detect it. Picture: Environet UK
Specially trained sniffer dogs can detect it. Picture: Environet UK

According to Environet’s research, around 5% of homes are currently affected by knotweed, either directly or indirectly, but sales can proceed as long as a professional treatment plan is in place.

Specially trained detection dogs can be brought in if an infestation is suspected.

Nic Seal, founder and managing director of Environet, said: “Japanese knotweed tends to strike fear into the hearts of homeowners but as long as they’re aware of its presence and take action to remove it before it causes any serious damage or spreads to a neighbour’s property, there’s no reason to panic.

"By publishing the 2022 hotspots for Kent we hope to raise awareness and encourage people in the area to be vigilant for signs of knotweed as the growing season takes off, so they can act quickly if needed.

"Anyone living near or moving to one of these hotspots would be wise to check their garden carefully, enter their postcode into Exposed to find out how many known occurrences are nearby and if in doubt, seek expert help.”

It first arrived in the UK in 1850. Environet UK
It first arrived in the UK in 1850. Environet UK

How to spot Japanese knotweed

  • Asparagus-like spears emerge from the ground in early spring and begin to sprout pale green leaves with distinctive pink veins
  • In May the plant starts to grow rapidly. The stems harden into bamboo-like structures and the leaves, which grow in a zigzag pattern up the stem, are lush, green and heart-shaped
  • By mid-summer the plant grows at a rate of around 10cm per day, with mature plants forming dense stands two or three metres tall
  • In August the plant blooms, with small clusters of creamy white flowers appearing on the upper leaf axials.
By mid-summer the plant grows at a rate of around 10cm per day. Picture: Environet UK
By mid-summer the plant grows at a rate of around 10cm per day. Picture: Environet UK

What to do if you think you have Japanese knotweed

  • If you find a suspicious-looking plant and you’re not sure what it is, you can check the identification guide on Environet’s website or use the free ID service by sending a photo to expert@environetuk.com
  • Once knotweed is confirmed, commission a professional Japanese knotweed survey to find out the extent of the infestation, where it originated and the best way to tackle it
  • Arrange professional treatment, usually herbicide or excavation, and always be sure to secure an insurance-backed guarantee for the work
  • Sellers are legally obliged to tell any potential buyer if a property has been affected by knotweed, even if the infestation has been treated
  • It’s not illegal to have knotweed on your land, but you will be liable if you allow it to spread to someone else’s property through inaction
  • If you’re buying a property and you want to be sure it’s clear of knotweed, particularly if it’s located in or near a hotspot, arrange a detection dog survey.
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