You may have heard the term “Japanese Knotweed” mentioned, but do you truly understand what it is and why it is such a serious concern?

This seemingly harmless plant, Reynoutria japonica (formerly Fallopia japonica), is an invasive perennial species originally from East Asia. It was introduced to Europe in the 19th century as an ornamental plant, valued for its vigorous growth and attractive foliage. However, its true nature soon became clear.

So, what exactly is Japanese Knotweed?

• Distinctive Appearance: It has bamboo-like stems, shovel-shaped leaves, and produces small, creamy-white flowers in late summer or early autumn.
• Rapid Growth: It can grow up to 10cm per day, forming dense thickets that outcompete native vegetation.
• Powerful Root System: Its rhizomes (underground stems) can extend up to 3 metres deep and 7 metres horizontally, making eradication extremely difficult.

Why is it so important to be aware of Japanese Knotweed?

1. Property Damage: Its aggressive root system can exploit weaknesses in foundations, drainage systems, paving, and even asphalt, leading to significant structural damage to buildings and infrastructure. This can result in costly repairs and devalue properties.
2. Mortgage and Sale Issues: The presence of Japanese Knotweed can make it very difficult to secure a mortgage or sell a property. Lenders often require a professional management plan in place before approving loans.
3. Environmental Impact: It outcompetes native flora, reducing biodiversity and disrupting local ecosystems. It can also cause erosion on riverbanks due to its shallow root system in such environments.
4. Legal Implications: In the UK, it is an offence to cause Japanese Knotweed to grow in the wild, and landowners have a responsibility to prevent its spread.

Using a RICS (Royal Institution of Chartered Surveyors) surveyor when purchasing a property is recommended as they can identify these plants and recommend further investigations before completing on a property transaction.    

Here’s how they can help:

Expert Identification and Assessment:

Accurate Identification: RICS surveyors are trained property professionals who can accurately identify Japanese Knotweed, distinguishing it from similar-looking plants. This is crucial because misidentification can lead to incorrect or ineffective treatment.

Severity Assessment: They can assess the extent and severity of the infestation, both above ground and, crucially, in relation to the property’s structure. This involves understanding the plant’s growth habits and its potential to cause damage.

RICS Categories: RICS has developed a specific assessment framework (updated in 2022) with “Management Categories” (A, B, C, D) that surveyors use to classify the risk posed by Japanese Knotweed. These categories provide a standardised way to communicate the severity to lenders, buyers, and sellers.

What should you do if you suspect you have Japanese Knotweed?

Do NOT try to tackle it yourself with herbicides or by cutting it down. This can often make the problem worse and accelerate its spread. Instead, contact a professional PCA (Property Care Association) accredited Japanese Knotweed specialist. They can accurately identify the plant and implement an effective eradication or management plan.

Understanding and identifying Japanese Knotweed is crucial for protecting your property, the environment, and preventing costly future problems. Share this post to help raise awareness and if you are worried that you have an infestation, give me a call.