The rampant invader
Brought to Britain by the Victorians as an ornamental plant, it grows up to 4in a day, penetrating walls and concrete
It is illegal to grow Japanese knotweed, allow it to spread or dispose of it incorrectly
The world’s most invasive species, it has no natural enemies in the UK
Roots must be killed, which is difficult, otherwise it regrows
It costs the economy £166million a year. Mortgages have been refused on properties with knotweed