The World Conservation Union marks it as one of the world’s 100 most invasive species of plant, and if you find it on a domestic property it can put an end to mortgage application. But what is Japanese knotweed and why is it such a problem?
What is it?
The plant originates in the Far East (hence the name) and was brought to Europe for its ornamental qualities. Although not related to bamboo, a flourishing knotweed plant can look very similar with its hollow stems and raised nodes.
Since arriving in Europe, knotweed has successfully adapted to the differing climate and is now growing out of control all over the continent.
Why is it a problem?
When managed properly, the plant itself is not too much of a problem. However, as managing it is a near impossible task, problems do abound. The root system of knotweed is strong and invasive meaning that it can spread through concrete foundations, roads, flood defences and the very walls of buildings.
Left to its own devices and not managed properly, a Japanese knotweed plant will cause almost irreparable damage to any structure.
Where does it appear?
Despite producing no seeds, the Japanese knotweed is an incredibly successful breeding machine. The plant reproduces from its underground stems (known as rhizomes) and, given the right conditions, can flourish and quickly multiply.
Once it is growing, the plant can outcompete almost all of its competitors meaning that hedgerows and other woodland species are soon strangled and starved by the invader.
There are several methods of removing Japanese knotweed and much depends on the quantity of the plant to be dealt with and the severity of the infestation.
Perhaps the most effective method of destroying the plant is the chemical solution. Spraying with what is essentially a weed killer attacks the plant from root to tip and should ensure that it is eradicated. The plant is known for being hardy and incredibly difficult to completely kill so even the chemical method may take a number of seasons.
Other methods include digging. If digging is done professionally, it can be very effective as digging out the roots stops the plant from reproducing. However, if the roots are not completely removed, the plant will soon come back leading to much frustration.
Burning the plant at source is another popular method but has varying levels of success.
Will it come back?
If treated properly and thoroughly, the Japanese knotweed should not come back. Beware, however, that although you may be free of one plant, another may start to grow in its place so keep your eyes open and be vigilant against the first sign of invasion.