Japanese Knotweed Damage : What You Need To Know


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Japanese Knotweed Damage And How To Minimise It

Japanese Knotweed is an aggressive and highly invasive plant, originally native to parts of East Asia, it was introduced to the UK in the 19th century as an ornamental plant.

Through soil movements, it has spread rapidly in certain areas, often with the more industrial ones being worse hit than others.

Millions of pounds per year is spent in the UK on Knotweed control and removal, with much of that spent addressing and preventing Japanese Knotweed damage.

Knotweed has become infamous because it can cause significant damage to foundations and infrastructure including drains, walls and pipes.

Japanese Knotweed also possesses the ability to outcompete both native and garden plants, significantly reducing local biodiversity and amenity value of outdoor spaces.

In this article, we’ll explain why Japanese Knotweed is a problem and what damage it can cause.


How Japanese Knotweed Spreads

Japanese Knotweed can spread quickly underground due to its ability to grow horizontally below ground at alarming rates.

The fast growing canes and wide leaves of Japanese Knotweed quickly overshadow and crowd out other plants and the roots run deep, usually to around 2 metres but we have seen it as deep as 3.5 metres.

The nature of the plant makes it extremely difficult for homeowners and property owners to control once it has become established.

Possibly Japanese Knotweed’s greatest competitive feature is its ability to regrow from even the smallest fragment of rhizome which means humans have unwittingly spread this plant across the UK and many other countries.

Coupled with Knotweed’s ability to grow through tarmac and masonry, you can see why Japanese Knotweed damage can lead to significant devaluation to residential and commercial properties and make them unsaleable without a Treatment Plan, Management Plan and Insurance Backed Guarantee in place.


Japanese Knotweed can damage walls and out buildings.

Japanese Knotweed damage on the rear of a local property.

Signs Of Japanese Knotweed Infestation

The most obvious sign that you have Japanese Knotweed on your property are the distinctive bamboo-like clusters of stems that suddenly spring up in early spring, the numbers and size depending on the scale and severity of the infestation.

These stems have distinctive green leaves with reddy-purple flecks and dense clusters of white flowers from August onwards.

These can grow incredibly quickly, reaching up to 10 feet tall and also have deep and complex root structures that penetrate several metres into the ground below.

In addition, Japanese Knotweed can also cause structural damage in a variety of different ways; garden walls can start to lean, tarmac cracks and paving slabs lift!

In extreme situations, the invasive and powerful roots are capable of breaking through masonry foundations and walls, being known to damage roads, pavements and even flood defences.


Japanese Knotweed damage is not confined to the built environment; the weed’s invasive and fast spreading nature coupled with its ability to grow quickly over a short period of time means that river banks can become completely dominated with a monoculture of Knotweed where nothing else green exists.

Their aggressive growth habit is also known to contribute to soil erosion, particularly on river banks which then releases more fragments of rhizome during periods of flooding with increased erosion.


What To Do If You Suspect Japanese Knotweed

Japanese Knotweed Root Damage

Japanese Knotweed roots are extensive and can damage foundations.

Acting fast is key when Knotweed is detected as any delay in treatment could allow the infestation to take hold. It is important, whether you have a domestic or commercial property, to be aware of not just the potential damage and removal of Knotweed but also the difficulties that may arise when selling the property.

It’s always best to get professional advice and at Clearsafe Knotweed we offer a free, no-obligation initial survey within 48 hours, so you can have peace of mind or start planning next steps.

We are also always happy to look at a photo to give you a quick opinion and you can book also video calls on our website if you would prefer.

If it is Knotweed, we will then act fast to get a plan in place to ensure the infestation is dealt with before any further spread or damage can occur; we can offer a full treatment and management plan along with an insurance backed guarantee or just individual treatments.


What You Shouldn’t Do

Only a few chemicals are approved for Japanese Knotweed treatment for good reason; diesel, hypochlorite and other industrial chemicals are certainly no better at killing Japanese Knotweed but they are much worse for the environment than purpose made herbicides.

Do not ‘re-purpose’ other chemicals for Japanese Knotweed treatment.

Do not try to attack the plant mechanically or with fire, it will do virtually nothing to reduce the strength pf the plant, it’s likely to spread plant matter that can regrow and there will also be no leaves left to treat with herbicides.


Actually the best thing you can do is to protect the plant until it is treated.

Do not move any soils or other plants from within a few metres of the plants to other locations, it may contain Japanese Knotweed rhizome which can regrow.

Do not pull stems out once they are dead, you may detach small pieces of rhizome that are then transported to a new location.

It’s better to cut or snap then off just above the surface; once they are completely dead and dried out they can be composted or left on the ground.

Remember, although the presence of Japanese Knotweed on your property can seem like the ‘end of the world’, with prompt action you can minimise any potential negative effects on your home or commercial property so give us a call today and let us get to the root of your problem.

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