What is Japanese Knotweed?

The wonderful nation of Japan have given us many great things over the years, from the Walkman to karaoke to electronic calculators, but one of the less helpful imports has certainly been the arrival of the Japanese knotweed plant.

So, what is Japanese knotweed you might ask? It’s actually a long-term resident of the UK, having been brought to the UK in the 1850s as a specimen at the famous Kew Gardens. It became a favourite of gardeners due to its bamboo-like appearance and ability to grow everywhere at a rapid rate, but that ability became a real negative over time.

You’ll no doubt be familiar with the expression ‘spreading like wildfire’, well in our professional capacity as Japanese knotweed specialists, we’d say that the phrase could have been invented for this plant and its impact on the UK!

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Spread like wildfire? Is it really that bad?

The ferocity at which Japanese knotweed makes inroads into gardens is nothing short of spectacular, with its unwelcome presence taking a stranglehold on many an unwitting victim’s garden.

While in its native Japan the potentially devastating proliferation of knotweed is largely controlled by a tag team of fungus and insects, here in the UK the resistance forces of Mother Nature doesn’t seem as effective in combatting its advances. So, with no known natural enemies to nip its forays in the bud, Japanese knotweed is left to run riot.

Japanese knotweed has a nasty (and recurring) habit of striking right at the heart of both domestic and commercial settings. Knotweed is certainly no respecter of locations, with the trail of damage it leaves in its wake often extensive. In statistical terms, it is measured that Japanese knotweed occupies at least one site in every 10 square kilometres of England and Wales on average, as well as being present across Scotland and Ireland.

So, we now know about the presence of Japanese knotweed, but we still haven't properly answered the question of what is Japanese knotweed? Let us explain a little more.

To refer to it with its Latin name, (which is only really ever done with plants these days!) Fallopia Japonica is a large, herbaceous perennial plant that is part of the knotweed and buckwheat family, Polygonaceae. As hinted above, it is - or rather, was - more commonly identifiable as being native to East Asia. You may have heard it referred to by some of its slang names such as fleece-flower, Himalayan fleece vine, monkey-weed, elephant ears, donkey rhubarb, sally rhubarb, Japanese bamboo or even Mexican bamboo.

Despite the monikers, it’s not linked to any of those animals, nor to rhubarb or bamboo. Nicknames aside, Japanese knotweed is prevalent in – as the name implies - Japan, and in China and Korea. The plant also racks up the air miles, now prevalent across areas of North America and Europe. Even Australia hasn’t escaped the spread of Japanese knotweed, although there it’s now classed as illegal to have any of the plant growing on your property.

How would I know if I had it on my property?

Once you have answered the question what is Japanese knotweed, the next step is reliably identifying it. In terms of its physical appearance and plant-like structure, Japanese knotweed features hollow stems (reaching a height of up to 10–13 feet each growing season) which comprise of distinctively raised nodes which can give it the look of bamboo to a casual observer, though it is not closely related. The leaves of the Japanese knotweed are best described as broadly oval with truncated base, while the flowers are compact and white or cream in colouration.

Perhaps most often noticed are the significantly smaller plants which prolifically spring up in unwanted places, for example those that sprout through cracks in pavements and which are most common in late summer and early autumn. Of course, it’s not just concrete pavements which fall victim to the persistence of Japanese knotweed and its aggressive encroachment on everyday terrains, as the plant is now equally at home in brick walls, tarmac and structural foundations, where its unrelenting ambitions and overwhelming strength sees the plant force itself upon a multitude of weakened surfaces.

Ok, but what damage can it actually do?

Should Japanese knotweed begin to appear on your property, it can rapidly cause damage to hard surfaces. Items under threat from knotweed include flood defences, as well as sites of historical/archaeological interest. Growth of Japanese knotweed can also cause aesthetic issues and reductions in land values where the plant rapidly grows. There is also the impact on insects and wildlife to consider, which due to the plant not supporting growth of our native insect species means it has no ecological value.

Then, and possibly most important for home and/or business owners, there’s the tangible financial risk to homes and businesses which can come with the Japanese knotweed territory.

It’s not unheard of for mortgages to have been refused on the grounds of the substantial presence of Japanese knotweed in the immediate surroundings of the property, or for thousands of pounds of damage to be caused to a home, whilst elsewhere local authorities are now perfectly within their rights to put a halt to the granting of planning permissions should Japanese knotweed be deemed to be a significant factor in the location!

This stance is likely to remain in place until the threat of the plant is eradicated. With direct reference to legality, under the Environmental Protection Act 1990, Japanese knotweed is legislatively confirmed as a ‘controlled waste’. By which it’s a stipulation that the weed is duly disposed of at licensed landfill sites. In the event of it being allocated to normal household waste, under the guidelines set out in Section 9 of the Wildlife and Countryside Act 1981, it’s an offence to ‘cause or allow the plant to spread in the wild’.

So, what do I do if I think I have knotweed on my property?

Well, as you can see, a plant that entered Britain under the disguise of being pleasant wildlife has actually caused some serious damage, so it’s important to know where you and your property stand.

You’d be well served looking at our Identification, Treatment and/or Removal pages if you think you might have an issue. We’re committed to all our clients getting quality professional services to guarantee they deal with the issue right, first time.

We hope that this initial look at the question of what is Japanese knotweed has been useful to you. To speak to JKSL in more detail about any of our services, you can call us on 0161 723 2000, or visit our Contact page to fill out our enquiry form.

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