Menace that spreads at 4 inches a day

Japanese knotweed (Fallopia japonica) was brought to Britain by the Victorians as an ornamental garden plant and to line railway tracks to stabilise the soil

The weed grows extremely quickly – up to 4in a day during summer

It is unlawful to allow knotweed to spread, or to dispose of it incorrectly

It has no natural enemies in the UK, but is controlled by fungus and insects in its native Asia. In 2010 experts introduced the Japanese bug aphalara itadori to the UK to try to eradicate it

It costs the economy £166million a year in treatment and home devaluations

People have been refused mortgages on properties because of knotweed