Japanese Knotweed (Fallopia japonica) has developed a well deserved reputation for being the most invasive plant in the UK.
It was first introduced to the UK in 1825 and spread to all the best Victorian gardens as a spectacular horticultural specimen. However by 1905 it had jumped the wall and was recorded on the spoil heaps of South Wales and since then it has spread the length and breadth of the country.
Its success is even more remarkable when it is realised that it has become such a menace without setting viable seed. The majority if not all the plants in the UK are clones of the first specimens imported, all the plants are female and need to be fertilised by a male plant which thankfully was never introduced. This means that this plant has spread by vegetative means alone obviously with the ignorant collusion of man.
It is difficult to control and can spread rapidly, it is capable of regenerating from small fragments of rhizome which are transported easily by modern development practices.
It is can cause damage to urban infrastructure, growing through tarmac and breaking concrete.
It is a threat to biodiversity out competing native species and monopolising local environments.
On riverbanks once it has died back in the winter the area is vulnerable to erosion.
It is scheduled in The Wildlife & Countryside Act 1981 and The Environmental Protection Act 1990.