With its red stems and deep green leaves, it is a pretty enough plant. But Japanese Knotweed Uk beauty
disguises the fact that it has become the scourge of British homeowners.
It grows at a ridiculous rate, is near-impossible to get rid of and has ruined house sales – wiping thousands off property prices.
Just this week, a woman told how nearly half the value of her aunt’s home had been wiped off by the plant growing on an adjoining piece of land.
Elizabeth Abraham’s Swansea home should fetch around £80,000 – but now the 91-year-old has been told it will not sell for more than £45,000 because of the untamed wild weed.
So what can be done about Japanese knotweed?
Here we tell you everything you ever wanted to know about it.
How did it get here?
Japanese knotweed UK, or Fallopia Japonica, was brought to Europe from Japan in the mid-19C by German-born botanist Phillipp von Siebold who found it growing on the sides of volcanoes.
Initially lauded for its beauty and potential as animal feed, and it was so celebrated that in 1847 it was named the “most interesting new ornamental plant of the year” by the Society of Agriculture and Horticulture at Utrecht in Holland.
In 1850, the Royal Botanic Gardens at Kew received a shipment from Siebold of various plants from his travels, including a sample of knotweed.
By 1854 the plant had been sent to the Royal Botanic Gardens in Edinburgh and was then sold commercially by nurseries.
The rest, as they say, is history.
How did it take over Britain?
Knotweed’s spread – through purposeful planting and it escaping – went undetected for years.
According to researchers at the University of Leicestershire, people sharing cuttings or disposing of unwanted plants was the “primary pattern of distribution.”
It was also spread through watercourses, and through the movement of soil for construction and road-building.
Knotweed expert Ann Connolly, who died in 2010, found one of the earliest examples of it being planted purposefully outside gardens was in Welsh coal-mining valleys in the 1960s and 70s as it was good for stabilizing the loose soil.
Why is it so problematic?
In its native Japanese volcanic landscape, the climate and regular deposits of ash would keep knotweed plants small, while the plant survived thanks to energy stores in its deep root system.
But in Britain, without these impediments, it grows unabated.
And at its most prolific it can grow up to 20cm EVERY DAY.
What can I do about it?
1. Dig it out.
Digging out Japanese knotweed UK is a possibility but leave any trace of its deep root system at your peril – it takes just 0.8g of root for a new plant to grow again.
2. Feed it to bugs
In 2010, experts introduced a Japanese bug, aphalara itadori, to the UK that feasts almost exclusively on knotweed.
3. Kill it with chemicals
You can turn to chemicals, especially treatments containing glyphosate, but beware: it can take up to five years’ treatment to finally be rid of the pesky plant.
Professional treatments can set you back thousands of pounds.