Japanese knotweed, the menace 4 in 5 don’t recognise

IT has a name which strikes terror into the heart of any property owner.

Japanese knotweed can take years and thousands of pounds to destroy after invading a garden. But four out of five people have no idea what it even looks like, it has emerged.

Only 19 per cent of people in Britain aware of the invasive plant, which can grow by four inches a day in summer, can identify it, a YouGov survey for knotweed removal firm Environet found.

It is often mixed up with plants from the same family which have heart-shaped leaves, such as bindweed and Russian vine.

It is even confused with common ivy, found in most British gardens and entirely unrelated.

Dr Trevor Dines, a specialist at conservation charity Plantlife,

‘It is a big plant but can hide easily’

said: ‘Japanese knotweed is an invisible giant. It is a big plant but it can hide itself very easily.

‘When it first appears, it is hardly there and it can take five to six years to get to the point that people notice it.

‘It disappears in the winter and it doesn’t have the big, blowsy flowers that some invasive species such as the rhododendron are known for. This is why it can be muddled up with other members of the same family.’

It has a lush green colour and zig-zag, purple-speckled stems. The shield-shaped leaves have a flat base. The rhizomes, or horizontal stems which produce roots, have white shoots. But cut the plant’s rhizome open and it will be bright orange inside.

In summer, shoots produce canes with purple flecks and creamy white flowers.