Also known as Fallopia japonica, this is a highly invasive plant which thrives around water sources such as ponds, canals and lakes, as well as in large open spaces. It is native to the East Asia in Japan, China and Korea. In North America and Europe, the species has successfully established in numerous habitats and is classified as an invasive species in several countries.
But most importantly, this plant can cause structural damage to homes and other buildings. It is strong enough to push through cavity walls and drains, and up through asphalt, cracks in concrete and driveways. It can also cause significant delays and costs to building development. When the plant invades natural habitats (often through fly-tipping), it out-competes and smothers other plants and animals that usually live there. It clogs up routes used by wildlife and takes up precious space along rivers and around hedges and roadsides.
In the UK, Japanese knotweed is established in the wild in many parts of the country and creates problems due to the impact on biodiversity, flooding management and damage to properties.
Another problem we have is that it can be time consuming and expensive to kill this plant. To eradicate the plant completely, the roots need to be killed. All above-ground portions of the plant need to be controlled repeatedly for several years in order to weaken and kill the entire patch. Picking the right herbicide is essential, as it must travel through the plant and into the root system below.
Some home owners in the United Kingdom are unable to sell their homes if there is any evidence of knotweed on the property! It has become such problem that, according to the UK government, the cost of controlling knotweed hit £1.24 billion in 2014.
Two years later, wild a Japanese psyllid insect was released into the wild in the hope of controlling and solving the problem. Controlled released trials began later on in 2016.
Particularly in the United Kingdom, Japanese knotweed has received a lot of attention in the press as a result of very restrictive lending policies by banks and other mortgage companies. Several lenders have refused mortgage applications after discovering the plant in their gardens.
The abundance of the plant can be significantly reduced by applying glyphosate, imazapyr, a combination of both, or by cutting all visible stalks and filling the stems with glyphosate.
We hope this article was helpful, and that you are now a little more informed about the dangers of this plant.
