The Damage That Japanese Knotweed Does

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Japanese Knotweed Damage – Causes, Effects & Dangers

Described in the UK as an aggressive and destructive weed, Japanese knotweed can cause a lot of underground and surface damage if it’s not properly managed. Causing weakening foundations and wider property damage, if you suspect Japanese knotweed is growing nearby, you should have it identified and removed before it becomes a costly problem.

Japanese Knotweed Property Damage

Despite being an ornamental plant when it first arrived in Europe in the nineteenth century, Japanese knotweed is considered a damaging and destructive plant. It can destabilise and weaken properties, fences, boundaries and flood defences through its rhizome system. It’s not an uncommon problem, but properties affected by Japanese knotweed will need to contact a specialist for identification and removal services to ensure the roots are entirely eradicated.

Japanese knotweed has a reputation as a potentially dangerous plant, which can grow rapidly and reach as tall as 10cm daily. It was even identified by the Environmental Agency (EA) as “indisputability the UK’s most aggressive and invasive plant”. As a result of its rapacious growth, Japanese knotweed will easily overwhelm a garden, affecting other local flora as much as any surrounding or nearby structure or substructure.

What Does Japanese Knotweed Look Like?

This pesky plant isn’t always easy to identify, and although it can look similar to bamboo, another invasive species which can require removal, they are not in the same family. You’ll recognise 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. To see what Japanese knotweed looks like, check out our pictures in our Japanese Knotweed gallery.

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What Damage Can Japanese Knotweed Do?

Rapidly growing and seeking 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 costly damage to buildings, foundations, pavements and even invade houses if they get in its way.

The power and speed of Japanese knotweed growth would almost be something to admire if it weren’t for the destructive nature of this weed. Difficult to contain and even harder to identify, Japanese knotweed will infiltrate even the smallest and thinnest of cracks and wind its way through drains and underground sewers.

Combined with its tenacity and resilience, Japanese knotweed brings a rapacious growth which makes it both dangerous and destructive for your garden and home. Japanese knotweed will target weak spots in buildings, crack masonry, split pipes and ravage foundations if left unchecked. It can also weaken fences and boundaries too, eagerly spreading from one garden to the next above or below ground.

Japanese Knotweed can damage:

Underground services – With its rapid growth, Japanese knotweed will work its way into pipes through tiny cracks or joints, and from there, it will expand, blocking the pipe and eventually breaking it.
Hard surfaces such as asphalt – This is the Japanese knotweed damage we see most often. Asphalt, patio slabs, and 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 walls – Again if 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.

Explore Japanese knotweed removal for homes or commercial properties.

Letting Japanese Knotweed spread

Failure to control Japanese knotweed on your property, and letting it spread to a neighbour’s garden can now lead to prosecution and quite a hefty fine for anti-social behaviour as well.

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).

But 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 individuals failing to control the troublesome triffid will have committed a criminal offence and be liable for a fine of up to £2,500. Not sure if it’s knotweed? Check out our article on plants that look like Japanese Knotweed.

Claiming damages for the spread of Japanese Knotweed

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 by 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.

What this means for you is that Japanese knotweed becomes your legal problem if it’s affecting your property. It’s also your responsibility, as identified by the UK government, to have it treated, removed and disposed of.

Stay safe and comply with the laws around Japanese knotweed. Discover more on the Japanese knotweed laws here.

The Cost of Allowing Japanese Knotweed to Spread

If you notice Japanese knotweed growing in a neighbour’s garden, it’s their responsibility to control it and make every effort to ensure that it doesn’t encroach into your property or another neighbour’s. Failure to do this means that they can be held responsible for damages caused by this invasive pest.

A case earlier this year between two neighbours was resolved after thirteen years, when a judge ruled Ms Line had allowed Japanese knotweed to encroach onto the Smith’s property. As a result the value of the claimants’ land had been reduced by 10%, from £800,000 to £720,000. Ms Line was ordered to employ reputable contractors over the next five years to eradicate the agricultural interloper and also to pay court costs. See more details of Smith v Line Japanese Knotweed case.

If you suspect Japanese Knotweed is affecting your property, get in touch today.

Surveying and Removing Japanese Knotweed

If you do suspect an infestation of Japanese knotweed on yours or your neighbour’s property, you can send us a photo for a free, no obligation check.

Once Japanese knotweed has been identified, you should tell your neighbours about it straight away and let them know that it is their legal responsibility to have the nefarious weed eradicated (if on their land). Then you should let them know about Japanese Knotweed Specialists, one of the UK’s leading contractors and consultants in the control, treatment, removal and thorough elimination of Japanese knotweed or give us a call on 0800 122 3326.