With its bright green leaves and bushy branches it looks harmless enough. But it's considered so dangerous that if it crops up in your garden you can be slapped with an anti-social behaviour order.
And cases of Japanese Knotweed are on the increase in the South.
The wee is estimated to cost the UK economy £166m a year and is so virulent, its roots can undermine foundations and bring down buildings.
In some cases, mortgages lenders have refused to offer to loans on houses where Japanese Knotweed is a problem.
If left untreated it can quickly dominate a garden and spread to other properties too. It's also an offence to plant or cause Japanese knotweed to spread in the wild under the Wildlife and Countryside Act 1981.
Common problems of the weed:
Damage to paving, tarmac and driveways
Damage to walls and foundations
Obstruction of light to windows and gardens
Damage to flood defences
Damage to archaeological sites
Displacing of native flora and fauna
Reduction in land and property values
The Environment Agency has published an online leaflet to help dealing with Japanese Knotweed that can be downloaded here.
Expert Mike Godfrey, from Japanese Knotweed Ltd, said that the roots often find their way along underwork pipes.
Watch Andy Dickenson's full report. He speaks with home owner Michael McNally, expert Mike Godfrey, and Simon Gerrard of the National Association of Estate Agents.