Everything You Need To Know About Properties With Japanese Knotweed

20/12/2018

Even if you don’t know its name, the Japanese Knotweed, you’ve most likely seen this plant. It has caused “difficulties” to realtors and homeowners to say the least and has spread almost globally. In this article, we’re going to outline facts, myths, and what to do with it if you have it on your property.

What we know about Japanese Knotweed

The Japanese Knotweed originates from East Asia. Its scientific name is now called Fallopia japonica, whereas before it was initially named Reynoutria japonica in 1777 Japan. The name has been lost in times and changed over the years due to new learnings and discoveries. This knotweed comes from the family Polygonaceae of the plant kingdom.

This plant can grow up to 4-5 inches per day if it is under favourable circumstances. That alone shows that it can turn into a nuisance if left unchecked for an extended period. In continents such as North and South America and Europe, it is widely regarded as a nuisance.

While the Japanese Knotweed has mostly originated from Korea, China, and of course, Japan, it has a counterpart that comes from Sakhalin Island, Korea, and Northern Japan. This is the Giant Knotweed (Fallopia sachalinensis).

How it came to be

The plant was brought to the UK in the eighteenth century by the German physician and botanist Philipp von Siebold. According to his studies, a justifiable term to describe this annoying plant is promiscuous.

Publications and molecular studies from another researcher, Dr. John Bailey from the Department of Genetics and Genome Biology of the University of Leicester in the UK, have found that the Japanese Knotweed comes from a single female clone.

This was found to be true at least in Europe, Britain, and the USA. This means that if we were to calculate the total biomass of the plant, we could conclude that it comes from the largest female organism in the world. Who would’ve thought?

Due to the lack of a male reproductive partner, it mates with other species it comes into contact with. In the West alone, you can find large strands of it. This, coupled with its extensive network of rhizomes underground, makes it very difficult to eradicate.

This plant has, without a doubt, caused a few problems. So much so that it has been known more as an infestation rather than a blessing to have. It can even deter potential property buyers once they discover this plant in the area.

How do I get rid of Japanese Knotweed?

There are numerous ways, but they can be summed up into three categories -- chemical, biological, and mechanical means. Any mixture of the three is also acceptable. There’s a myth circulating that all solutions are expensive. We’re happy to debunk that; it is actually only the chemical approach that can cost a pretty penny.

Just keep in mind that there are still pros and cons to each! After all, this plant was uprooted from the volcanic ashes near Nagasaki, Japan. There, it persevered amidst the poison gas excretions and lava. Any plant that has that kind of background is sure to be resilient.

The chemical approach, although valid, does not guarantee success. Not to mention the potential harm it can cause to its immediate surrounding environment. The recommended way is to use herbicide while also physically cutting off the sprouts until you get to its roots. This method may take you a long time to completely eradicate it, especially if the strands have already established themselves over time.

Physical removal might be the best option. However, depending on the size of the infestation, you might need to hire help. Doing it all yourself can be highly taxing and laborious. Also, physically removing the rhizomes can produce a lot of hazardous waste.

This waste must then be taken to a specific landfill site that can handle the deposition of live Japanese Knotweed rhizomes. This specific procedure is due to the Wildlife and Countryside Act 1981. It is an offence to intentionally and knowingly spread this plant “in the wild.”

However, a new method is being developed. Biological control using the bug that sucks plants, also known as the Jumping plant lice or psyllids is being researched and developed. It’s still in its trial phase; however, if it proves successful, it will be commercially available to gardeners in the UK.

It seems that whichever method you choose, there isn’t a perfect option. Thus, the key to getting rid of this plant if found in your property, at least for now, is due diligence, patience, and perseverance.

Myths

“Japanese Knotweed can damage the foundations of buildings and can grow in between concrete.”

Not only is this a myth, but unrealistic. As a matter of fact, professionals like the PCA (Property Care Association) use only reinforced plastic to mitigate and control the Japanese Knotweed to prevent it from getting out of hand.

However, what’s closer to the truth is that the Japanese Knotweed can manoeuvre through gaps in surfaces like brickwork or paving. It doesn’t grow through them; instead, it can exploit the crevices and, over time, can start to root from there. The roots and stems can then exert force as they expand over time. This is more likely to be the reason they would potentially cause damage.

“The Japanese Knotweed has seeds alongside its roots. That’s why it has a pervasive root network.”

No. This plant does not produce seeds. The roots are the only way for it to spread.

Early detection is key

Fun fact: this plant is one of the ten most invasive plants in the UK.

Thus, it is imperative that you identify the Japanese Knotweed if you suspect it is in your home. As mentioned before, there are laws and regulations regarding it, but apart from all that, it can be an absolute pain to remove when it has grown too much.

There will always be means and ways, and even professionals (depending on your area) that can do the job. However, as with our health, prevention will always be better than cure.

If the problem has become large already, keep a cool head. All you have to do is take it day by day.

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