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02.07.2019, 13:11

Managing Japanese Knotweed

White Papers & Briefings, EMEA
Adam Brindle, managing director of UK grounds contractor, The Grounds Care Group, explains the challenges for facilities managers of eradicating one of the most pesky of plants.



The Japanese have long provided the UK with a wealth of precious commodities, from reliable cars to ingenious electronics. However, one of their least welcome exports (notwithstanding karaoke!) that has made its way to our shores is Japanese Knotweed.

 

This most troublesome guest began its UK staycation in the 1850s when it wowed Victorian botanists with its exotic appeal, and soon became commonplace in any well-to-do garden. However, modern gardening trends soon moved on and this horticultural flavour of the month, and its resilient roots, were discarded by the wayside. 

Little did the gardening gurus of the day know, they were actually unleashing a fiendish devil weed into the wild, since Japanese Knotweed can regrow from just a 2mm fragment of root, that’s just what it did. The inhospitable rocky terrain of the quarries and roadsides where it was dumped were nothing to this voracious vine that found its origins on the hostile slopes of volcanoes in Japan. 

 

Today, 150 years on, it remains the blight of modern day facilities and property managers up and down the country.

 

The pesky plant isn’t always easy to identify, and although it can look similar to bamboo, they are not in the same family. You’ll know Japanese Knotweed by its spade-shaped leaves, which can grow up to five and a half inches in length. During the late summer, it can also be identified by its creamy-white flowers.

 

On its never-ending search for growth and sustenance, Japanese Knotweed can grow through brick walls and even concrete when it finds a weak spot. And as it makes its way, it’ll cause untold damage to buildings, foundations, pavements and even invade properties if they get in its way. 

 

The power and speed of Japanese Knotweed would almost be something to admire if it weren’t for the destructive nature of this villainous weed. Ever eager to expand its territorial domination, Japanese Knotweed will infiltrate the tiniest of cracks and wind its wily way through drains and underground sewers. 

 

Combined with its tenacity and resilience, Japanese Knotweed brings a rapacious growth which makes it a truly unwelcome garden guest and an even less welcome property invader if you’re unlucky enough. Able to grow up to 10 cm a day, Japanese Knotweed will target weak spots in buildings, crack masonry, split pipes and ravage foundations if left unchecked. And it shows no respect for fences and boundaries either, eagerly spreading from one garden to the next above or below ground. 

 

Common headaches faced by FMs

Underground services – With its insatiable thirst, Japanese Knotweed will worm its way into pipes through tiny cracks or joints, and from there it will expand locking the pipe and eventually breaking it.


Hard surfaces such as asphalt – This is the Japanese Knotweed damage we see most often. Asphalt, patio slabs, driveway block paving will pose no problem to Japanese Knotweed on its unstoppable quest for light. Basically, if water can drain down into it, Japanese knotweed can grow up through it.

 

Concrete – It may be strong but not even Japanese Knotweed can grow through concrete. It normally finds a weak spot, pushes through and then expands as it goes to cause damage. 

Buildings – If left unchecked for long enough, Japanese Knotweed can establish itself and wreak havoc on residential and commercial properties.

 

Boundary wall – Again is left unchecked, Japanese Knotweed will grow with enough force to damage fences and even cause walls to fall.

 

Cavity walls – Japanese Knotweed will grow up and through vents and air bricks two metres above ground, and once it’s in cavity walls it has the force to push the two skins of the wall apart.

 

Your legal responsibility

As an FM you may have a legal responsibility for the containment and safe disposal of Japanese Knotweed. Failure to control its spread to a neighbouring property can now lead to prosecution and a hefty fine for anti-social behaviour as well. 

 

In the United Kingdom, Schedule 9, Section 14 of the Wildlife and Countryside Act 1981 states that “if any person plants or otherwise causes to grow in the wild any plant which is included in Part 2 of Schedule 9, he shall be guilty of an offence”. (Japanese knotweed is a Schedule 9 listed plant). 

 

However, updates to the guidance documents now specifically name Japanese Knotweed alongside Himalayan Balsam and Giant Hogweed as a source of “serious problems” and state that an individual failing to control the troublesome triffid will have committed a criminal offence.

 

Indeed, the government has reformed the Anti Social Behaviour, Crime and Policing Act 2014, so that community protection notices can be used against individuals who are acting unreasonably and who persistently or continually act in a way that has a detrimental effect on the quality of life of those in the locality. Meaning if you fail to deal with the problem you could end up with an ASBO!

 

For corporates the cost on non-compliance can run into the tens of thousands of pounds, indeed we have heard of one case involving just 1sqm of knotweed which resulted in an out of court settlement £50,000. Due to the significant pay outs involved, it is no surprise that lawyers are jumping in on the act and also using private nuisance laws to pursue claims.

 

In 2013, Stephen Williams and Robin Waistell, two residents in South Wales made a claim against Network Rail, which owned the land immediately behind their properties. Japanese Knotweed had been present for at least 50 years on the land owned Network Rail. The neighbours complained about the encroachment on to their land, and were awarded damages when the judge ruled Japanese Knotweed as a natural hazard affecting landowners’ ability to fully use and enjoy their property. The interesting thing about this case, was that it re-defined the word ‘damage’, in so much as no physical damage had to take place, but merely the presence of just the root in a neighbouring land was classed as damage.

 

Surveying and Removing Japanese Knotweed

Japanese Knotweed is a difficult and tenacious plant, and getting rid of it can be a complicated and time-consuming process. If left untreated, it will spread quickly and the dame it can cause damage to foundations and buildings can be extremely costly. 

 

Getting rid of Japanese Knotweed is not easy, and the best solution is to contact a professional removal company as soon as you have identified it on your property so that an effective maintenance or removal plan can be established. Of course, as Knotweed removal specialists, we would say that! But if you are considering tackling the problem yourself, here are a few things you need to know. 

 

Japanese Knotweed can grow up to 10 cm a day with roots burrowing down as deep as 3 metres. For this reason, it is important to get started on remove it as soon as possible. 

 

No infestation of Japanese Knotweed is the same. Different solutions for removing Japanese Knotweed include herbicide treatment, stem injection, excavating infected areas of ground with machinery, or a Japanese Knotweed root barrier to halt the spread of the irksome weed. 

 

Once removed, Japanese Knotweed needs to be disposed of to ensure it can’t regrow. Off-site burial can be expensive since the soil is classified as controlled waste in many countries, including the UK where sifting and screening services are often called in to remove fragments of the root and rhizomes from soil.

 

 

 

 

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