Why is Japanese knotweed such a problem?
Japanese knotweed is not native to Europe and was introduced to the UK without its natural enemies. In Japan, the plant generally grows in harmony with the environment and is not considered to be invasive. One could say it has an unfair advantage over native species because the controlling influence of the many insects and fungi that attack the plant in its native range has been removed. Our native species have not taken a shine to knotweed and very few if any insects or fungi can be found on the plant even after almost 200 years. A recent estimate put the cost of control, were it to be attempted UK-wide, at over £1.5 billion. Such control methods, relying mainly on chemicals, are widely considered to be unsustainable and so a longer-term and cost effective solution to the problem is required.
