Japanese Knotweed was introduced to this country in the 1800s as an ornamental plant. It was noted however as early as the late 1800s that the plant was invasive but by this point had been distributed widely. As its natural enemies of -presumably Japanese - insects and fungi do not exist over here in Blighty it spread and spread it did… being able to cause structural damage to property and grow through tarmac.
Although the nature of Japanese Knotweed was noted early on it wasn’t until the Wildlife and Countryside Act 1981 that it became an offence to cause Japanese Knotweed to grow in the wild. Whilst it is not illegal to have Japanese Knotweed in your garden, under the Anti-social Behaviour, Crime and Policing Act 2014 (yes seriously) a community protection notice can be used to require someone to control or prevent the growth of Japanese Knotweed (or other plants) capable of causing serious problems to communities. As such if there is Japanese Knotweed in your garden you should keep it under control, however it cannot be simply be cut and put in the garden waste bin as under the Environmental Protection Act 1990 Japanese Knotweed is classed as ‘controlled waste’ and needs to be disposed of at licensed landfill sites.
As you can imagine mortgage lenders are cautious of Japanese Knotweed and if it is present in a house you wish to buy you will need to consider carefully how to eradicate it and the cost involved as it will probably affect the marketability and value of the property. I once acted for a buyer whose lender made a 100% retention and required all kinds of guarantees from the company that removed the Japanese Knotweed before they would release any funds. The Japanese Knotweed was not even in the boundary of the property but in the land behind. Needless to say my clients decided not to proceed with the purchase.
Unfortunately Japanese Knotweed does not resemble Audrey from The Little Shop of Horrors and Japanese Knotweed looks fairly harmless, but looks can be deceiving so call in the experts…