What is Japanese Knotweed?
Japanese Knotweed is the most invasive plant known in Britain today. The plant originated in Japan where it thrives on disturbed ground. Knotweed was introduced to the UK in the early 19th Century as an ornamental plant also being used as a feed crop for cattle. The Victorian Horticulturalist who introduced the plant cannot have envisaged the devastating impact Japanese Knotweed would have.
It is effectively a giant herbaceous perennial which grows at an alarming rate of up to 10cm per day in any type of soil. It forms dense clumps of up to 3m (10ft) in height. Japanese Knotweed thrives on disturbance and spreads by natural means and by human activity. Very small fragments of rhizome (underground stems), as little as 0.7g - approximately the size of a fingernail - can produce fresh new plants. But it is below ground where this invader causes the biggest problems, as each stand creates a rhizome network that can extend to 3m in depth and 7m in all directions. This makes it a serious threat to construction where it can have devastating consequences damaging foundations, drains and other underground services.