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Property Surveying Blog
Written by Berry Lodge Surveyors

Invasive species have always been a problem in the United Kingdom. At current there is a varied mix of invasive species ranging from plants to bugs and even frogs!

Japanese Knotweed

Invasive species tend to be a problem as they are not only able to out compete the native species: They also don’t have the same natural ecological controlling factors that would be present in their natural environment and therefore often thrive in a new environment, as is the case with Japanese Knotweed.

So let’s take a brief historical look at Japanese Knotweed

A Victorian Botanist, Philippe von Siebold, first introduced Japanese Knotweed into the United Kingdom from Japan in the 1800’s as an ornamental garden plant.

Japanese Knotweed With heart shaped leaves and purple speckled stems, the plant was considered attractive by many. One of the most commonly accepted theories on the prolific spread of Japanese Knotweed throughout the United Kingdom, is that like minded individuals who found the plant attractive would often share cuttings and as such the plant spread to its current point.

Irrespective of where you are currently located, so long as you are reading this blog post from within the UK, Japanese Knotweed is so widespread that it is said to be present within 6 square miles of wherever you stand.

So what is the problem with Japanese Knotweed?

This fast growing invasive plant, which in the summer months can grow up to 5 inches a day, presents a serious risk to existing properties and new construction projects.

Japanese Knotweed’s roots can grow through underground clay drainage pipes, push through brick walls and can even grow through 3 to 4 inches of concrete and tarmac.Japanese Knotweed

Needless to say, if Japanese Knotweed is present on your property or even on a neighbour’s property, you are at a real threat of the lender refusing to offer you a mortgage. At the very least the existence of the plant will likely reduce the value of the property by a significant amount.

In the event that Japanese Knotweed is noted, its removal and eradication is imperative to preserving the value of your property and ensuring that you are not a party to legal action taken by a neighbour.

So how can I recognise Japanese Knotweed?

The first step to eradicating this potentially damaging plant is identifying it in its earliest stages. The quicker you identify it, the quicker you can treat and remove it.

There are a number of unique characteristics that make Japanese Knotweed an easy plant to identify;

The Stem

In the Summer months Japanese Knotweed’s stem is light green with reddish to purple blotches. During the winter months, from October to December, the stem will often turn a brown to dark brown tone.Japanese Knotweed

The stem of this prolific plant grows in a zig-zag pattern with a heart shaped leaf growing at the junction of each respective zig-zag.

Japanese Knotweed has a bamboo like, hollow stem which when snapped off has a satisfying ‘POP’ sound! Due to the potential risk of spreading the plant we don’t recommend you try this.

Japanese Knotweed Leaf

The leaves begin as a deep red sprout and as they grow they gradually change to a lush green colour.

The leaves are distinctly heart or spade shaped, with either a flat bottom or two lobes tapering to a sharp defined point.

How to remove and eradicate Japanese Knotweed

Unfortunately, Japanese Knotweed is incredibly costly to remove. On average over 166 million pounds is spent a year nationwide on its removal and treatment.

In addition, Japanese Knotweed is also classified as a controlled waste product, which means that it must be disposed of in a responsible manner, with fines up to £5,000 issued in the event of a breach!

Japanese Knotweed methods of removal

With it being known to survive burning and being able to grow back within days of it being cut down, on face value it may seem impossible to effectively eradicate the plant. However, there are some tried and tested methods available.

Large-scale excavation

Digging out the roots to remove all traces of the plant can be an extreme but quick method of eradication.  This method is usually employed on a large development sites, however it is worth noting that one plant alone will require up to 21m3 of soil being excavated and removed.

Weed Killer or Herbicide

As Japanese Knotweed is a plant, commercial weed killer will affect it. However, it can often take up to 5 growing seasons of treatment to fully kill and thereby eradicate it.

Japanese Knotweed Treatment is usually in the form of spraying the leaves, or directly injecting the stems of the plant with a high concentration of Glyphosate weed killer.

Japanese Knotweed is quickly becoming one of the most typical issues our surveying team identify on site, this year alone with have noted the presence of Japanese Knotweed on over 10 residential properties within London.

If you spot Japanese Knotweed on your own property, get in contact with an insured Japanese Knotweed Removal Specialist as soon as possible, ignoring the issue will likely only lead to higher removal costs.