Know vine enemy: What is Japanese knotweed?



June 07, 2022

Japanese knotweed goes the extra mile as the UK’s worst weed, but what is it exactly?

Know vine enemy - Japanese knotweed

What is Japanese knotweed

Japanese knotweed (or Asian knotweed) is a weed, but not your average garden weed! In fact, it can grow as much as 10cm a day in the summer – as tall as a can of Coke!  From the Polygonaceae family, its scientific name is 'Reynoutria japonica' or 'Fallopia japonica'. 

Japanese knotweed is also an invasive, non-native weed. This means it doesn’t originate from Britain. Actually, a chap named Philipp von Siebold brought Japanese knotweed to the UK in 1850.

Today, Japanese knotweed grows near and around rivers, railway lines, gardens, council-owned areas (such as cycle paths and playing fields) and where there is a lot of fly-tipping.

As a herbaceous perennial, Japanese knotweed will return every year until it is properly treated or removed. There is no rest for this wicked weed!

What does Japanese knotweed look like? 

As with other perennials, the plant changes in appearance dramatically from spring to winter. 


Spring appearance of Japanese knotweed
In Spring, the Japanese knotweed shoots emerge from the ground with reddish/purply stems and leaves, somewhat resembling asparagus.  


Summer appearance of Japanese knotweed
In Summer, it is tall and bamboo-like, boasting large shield shaped green leaves and clusters of creamy white flowers.


autumn appearance of Japanese knotweed canes
In Autumn and Winter the leaves and canes will brown and “die back”, disappearing underground until its cycle starts again next spring.

Why is Japanese knotweed such a problem?

In short, Japanese knotweed causes money and mortgage problems by damaging your land as well as commercial and residential buildings. It has no trouble growing through brick and mortar, pipework, drains, tarmac, concrete, foundations, sheds and even conservatories! 

Annoyingly, mortgage lenders and potential buyers tend to avoid land affected by Japanese knotweed. Even more annoyingly, knotweed will take 20% off the value of your property as well as cost thousands to remove.

Japanese knotweed is such a danger to property that the government have put laws in place to prevent it from being spread, and it can even cause legal battles between neighbours!

Japanese knotweed removal

Japanese knotweed will only be eradicated if you kill it with herbicide (poison) treatments or dig it out and take it to the dump. Either way, it’s a financial thorn in your side!  

But take heed. Unless you are a registered Japanese knotweed removal expert, don’t try to remove the plant yourself. And we’re not saying that because we’re a knotweed removal firm! The fact is, the more you disturb Japanese knotweed, the more plant fragments will “fall on the wayside” and spread. Many of our clients get frustrated because they believe they have finally removed an infestation, only for it to return next year.

It’s important you let experts – with the right equipment and understanding of knotweed law – help you avoid liability and even the police!  Better wash your hands of it and let the experts in!

Contact us now to discuss Japanese knotweed on your land.