Japanese knotweed was introduced into the UK for ornamental purposes in the mid-1800s but its rapid and widespread growth has become a country-wide problem, according to the Environment Agency, and it now costs the UK economy about £165m a year to try and stem its spread.
Knotweed now takes the top spot on the Environment Agency’s list of the UK’s most invasive plant species, and is described as ‘indisputably the UK’s most aggressive, destructive and invasive plant.’
Among its lengthy list of unappealing characteristics is the fact that it outgrows most other native flora, contributes to river erosion and spreads rapidly – growing 3m high during a typical summer. It can also push through asphalt, cracks in concrete, driveways, cavity walls and drains in its search for light and water.
It has spread rapidly throughout Britain, and local authorities are well aware of the problem, reporting infestations at various locations, including in green spaces and private properties.