Is Japanese knotweed posing a threat to your home and garden?

Latest data has revealed the places in Suffolk that are suffering the most from the invasive species.

Although the plant is currently in winter hibernation, it can pose a risk to property owners by knocking as much as a tenth off the value of homes.

Japanese knotweed can grow up to three metres in height by mid-summer, pushing up through concrete, driveways, drains and the walls of houses.

Data compiled by company Environet UK on its Exposed tracker has found Ipswich topped the rankings for the most infestations in the county, with 49 recorded within a 4km radius in the north of the town.

In comparison, the next highest, Beccles, had 29 recorded infestations.

East Anglian Daily Times: Japanese knotweedJapanese knotweed (Image: PA)

Lowestoft ranked third-highest with 27 infestations, while Stowmarket had 20 and Halesworth had 12.

Here is a list of every town in Suffolk and the number of Japanese knotweed sightings reported within a 4km radius as of January 2023:

  1. Ipswich - 49
  2. Beccles - 29
  3. Lowestoft - 27
  4. Stowmarket - 20
  5.  Halesworth - 12
  6.  Leiston - 8
  7.  Aldeburgh - 8
  8.  Sudbury - 7
  9.  Bury St Edmunds - 7
  10.  Eye - 6
  11.  Woodbridge - 6
  12.  Haverhill - 6
  13.  Saxmundham - 5
  14.  Felixstowe - 4
  15.  Needham Market - 4
  16.  Hadleigh - 3
  17.  Mildenhall - 3
  18.  Southwold - 3
  19.  Framlingham - 1
  20.  Newmarket - 0

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

East Anglian Daily Times: A map of Japanese knotweed hot spots across SuffolkA map of Japanese knotweed hot spots across Suffolk (Image: Environet)

Favoured for its rapid growth and pretty 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.

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

East Anglian Daily Times: Japanese knotweedJapanese knotweed (Image: PA)

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

While serious damage to property is rare thanks to regulation which requires knotweed to be dealt with when a property is sold to a buyer using a mortgage or if it encroaches across a garden boundary, it commonly impacts use of the garden, causes legal disputes between neighbours and can impact a property’s value by around 5%.

People who spot an infestation, characterised by the plant's purple or red asparagus-like shoots, can mark it on Environet UK's online map, with each picture verified by experts.