The History of Japanese Knotweed
In the long, controversial, and chequered history of Japanese knotweed, one man - Philipp Franz Balthasar von Siebold – has more to answer for than anyone else. In 1850, the German botanist and doctor sent a surprise package to Kew Gardens containing several unusual plants from the Far East. He could never have imagined this generous and seemingly innocent act would have such far-reaching consequences that exist to this day.
Von Siebold was a renowned physician with a passion for plants and had spent six years in Japan collecting around 2,000 specimens which he brought back to Europe. Among the specimens was a hardy shrub found across Asia and valued for its rapid growth, medicinal properties, and uses as a vegetable in cooking.
It wasn’t long before von Siebold set up a company specialising in unusual plans and one of his biggest sellers was Japanese knotweed. It was marketed as a new, Asian, ornamental plant and was so sought after that its price began to rocket. It was at this point that von Siebold decided to tell the rest of the world about Japanese knotweed, so off went his package with a specimen to Kew Gardens.
The History of Japanese Knotweed – the Rapid Rise in Popularity
Victorian Britain looked very different to how it is now with its plethora of stately homes, enormous estates, and vast, landscaped gardens. Wealthy landowners were quickly bowled over by the new Japanese plant and its multiple uses. Not only was it a hardy, ornamental plant, but its rapid growth meant swathes of land could be covered and long borders created in very little time. The way it grows in clusters helped stabilise sand dunes and protect land, and it had numerous other uses such as cattle feed, matches, decoration and more.
The rest of the world would eventually wake up to the benefits of Japanese knotweed and it was soon a common sight across most of Europe, North America, and Oceania. As its roots quickly established themselves, many of the original knotweed clusters from the 19th Century still exist today in the same location where they were first planted. This is a clear indication of the extreme strength of knotweed, its relentless growth, and just how difficult it is to remove and eradicate.
Sadly, as pretty as those Victorian estates and gardens adorned with Japanese knotweed may have looked, the seed had been planted and the battle to control its seemingly unstoppable spread had begun.
The History of Japanese Knotweed – How a Plant Got Out of Control
Mass planting of Japanese knotweed had taken place during those Victorian times, and it was more than enough for the plant to establish itself on British soil. So, aside from von Siebold’s initial introduction, it was humans who then propagated its spread with vigorous planting without so much thought about the potential consequences it may have to our own native plant species and other natural ecosystems.
But it was too late. Japanese knotweed had already taken a firm foothold, and it was not about to let go. Von Siebold’s company may have listed knotweed’s “inextirpable” nature as one of its beneficial qualities, but that view would gradually change over time and turn into the modern-day nightmare that it is.
If only von Siebold had paid attention to the early warning signs. After all, knotweed is an indestructible invader whose roots can grow up to 20cm per day, while it can also reach 10 feet in height. Its natural habit is the harsh, often toxic environment of volcanic slopes. When an eruption takes place, guess which plant is among the first to regrow? You’ve got it – Japanese knotweed. And why? Because the same irrepressible root system – or rhizome – that can penetrate concrete and building foundations can also take hold in solid volcanic rock. There, it will survive for decades and longer, even when its shoots and leaves above ground appear to have been destroyed.
Back in 21st Century Britain and Japanese knotweed has become incredibly difficult to beat and control. Its impressive ability to survive and even lay dormant for 20 years before regrowing has helped this invasive species spread and expand at an alarming rate. It’s taken hold in a variety of settings like suburban gardens, railway verges, and canal systems, and will keep on growing into every available space it can.
While the leaves and visible parts of knotweed die each winter, the following spring will see new root growth, rapid, lateral expansion, and an abundance of fresh, asparagus-like shoots, stems and leaves above ground, forcing out other species as it spreads and causes widespread damage.
The History of Japanese Knotweed – What the Future Holds
All Japanese knotweed plants found in Europe are clones of a single, female specimen that is thought to be genetically identical to the one which von Siebold sent to Kew Gardens.
Britain is home to several species of Japanese knotweed including giant knotweed and dwarf knotweed, though Fallopia japonica is by far the most common. None of it grows from seed as all the plants are female. Yet, even though female Japanese knotweed plants are still looking for a male mate, they are capable of hooking up with their giant and dwarf versions, producing a hybrid called bohemian knotweed which many believe could be the most invasive knotweed of all.
Thankfully, bohemian knotweed is rare in the UK but is widely found in parts of Europe and North America. It is this ability to hybridise that worries experts most, as one day it could produce a male Japanese knotweed plant and the perfect mate for Europe’s solitary female. Should that happen, and offspring appear, we will have a greater fight to control Japanese knotweed than ever before.
The History of Japanese Knotweed – What if I Have Japanese Knotweed?
Firstly, there is no reason to panic. Japanese knotweed is the UK’s most invasive plant species and is listed as a controlled plant under the Wildlife and Countryside Act 1981. It is possible to remove, treat, and control it if you find it on your property, though it is advised to use a professional Japanese knotweed removal service rather than do the work yourself.
Identifying knotweed can be difficult as it closely resembles other plants. Unless you know your knotweed from your bamboo, it is best to get the experts in. If you fail to do this, you could be left with a knotweed infestation that can grow through cracks in concrete and masonry and even damage the foundations of a property.
Removing knotweed must be done with extreme care as it essentially involves removing the land itself. Following that, safe disposal of knotweed is essential as leaving behind even a tiny root fragment weighing as little as 0.3g is enough for it to regenerate and regrow over time. It could also lay dormant for 20 years before springing back into life and wreaking havoc once again.
Though it is not illegal to have Japanese knotweed on your land, it is against UK law to allow it to spread onto a neighbouring property or into the countryside. Japanese knotweed infestations can have dire financial consequences too as its presence has been known to devalue property and put mortgage lenders off.
Are You Concerned by the Presence of Japanese Knotweed on Your Land?
Given that Japanese knotweed could prevent you from selling your property, the quicker you take action for its removal the better. Our expert team at Japanese Knotweed Specialists will identify knotweed and then devise a plan for its treatment, removal, and disposal that includes a 5 or 10-year insurance-backed guarantee. So don’t wait and allow Japanese knotweed to spread, arrange for a survey today.