Japanese Knotweed season is here: Find out everything you need to know

·3-min read
Explosive reports have revealed the extent of Japanese Knotweed in the county
Explosive reports have revealed the extent of Japanese Knotweed in the county

EXPLOSIVE reports have told of the horror that Japanese Knotweed can unleash on homes.

The most infamous species of the knotweed family has been known to tear down buildings and is notoriously difficult to get rid of.

Only last year, homeowners in the Amman Valley, Carmarthenshire won compensation after successfully suing Network Rail when the plant encroached on their gardens.

The owners won a staggering £42,500 in damages.

Japanese knotweed is one of the five most common plants that could devalue your home.

It is considered one of the most invasive and hardest plants to remove.

The plant can grow up to three meters tall and its roots can reach down to 20 meters underground.

This means the weed can be destructive to pipework and drains and could even weaken building foundations and lead to potential foundational collapse.

It’s estimated the plant can take a 5 to 15 per cent off the value of a property.

Western Telegraph: Environet UK has revealed the knotweed hotspots for Spring using data from its online map
Western Telegraph: Environet UK has revealed the knotweed hotspots for Spring using data from its online map

Environet UK has revealed the knotweed hotspots for Spring using data from its online map

Recent data revealed the Pembrokeshire hotspots where Japanese Knotweed is running wild.

As the Japanese knotweed growing season gets underway, invasive plant specialist Environet UK revealed the knotweed hotspots for Spring using data from its online map.

The areas around Cwm Gwaun and Fishguard are the worst impacted areas in Pembrokeshire, where there are up to 220 occurrences of Japanese Knotweed in a 4km area.

Some of the worst affected areas include Dinas Cross, and Newport areas.

Haverfordwest, Saundersfoot and Carmarthen are also registered as hotspots.

Western Telegraph: Last year over £40,000 in damages was paid out for Japanese Knotweed encroachment in Pembrokeshire
Western Telegraph: Last year over £40,000 in damages was paid out for Japanese Knotweed encroachment in Pembrokeshire

Last year over £40,000 in damages was paid out for Japanese Knotweed encroachment in Pembrokeshire

The plant is most commonly found near railway locations as it was traditionally used to support railway embankments and their surroundings.

If the plant has grown up to a metre onto a property or piece of land, owners could be entitled to make a claim.

There are currently almost 55,500 known occurrences of Japanese knotweed in the UK but how did a plant originating from Japan end up in the country?

It was largely believed European adventurer Philipp Franz von Siebold transported Japanese knotweed over to Europe from a Japanese volcano.

In a 1850, a specimen from the plant was donated to the Royal Botanic Gardens in Kew, London.

It was favoured by gardeners because it looked like bamboo and grew everywhere.

It is largely thought the weed travelled rapidly across the UK, aided by rail and water networks.

How to spot Japanese Knotweed

Knotweed hibernates over winter but in March or April it begins to grow, with red or purple spear-like shoots emerging from the ground which quickly grow into lush green shrubs with pink-flecked stems and bamboo-like canes.

For homeowners, the plant can pose serious problems if left unchecked, with the potential to grow up through cracks in concrete, tarmac driveways, pathways, drains and cavity walls.

The roots can grow as deep as three metres and spread up to seven metres horizontally. While serious damage to property is rare thanks to regulation which requires knotweed to be dealt with, it commonly impacts use of the garden, causes legal disputes between neighbours and can impact a property’s value by around five per cent.

Why is Japanese Knotweed so notorious?

Japanese knotweed has acquired a reputation as one of the most invasive plants which is known to cause damage to properties.

It is also notoriously difficult to kill – root systems can extend up to three metres deep and leaving even just a few centimetres of root behind will result in the plant quickly growing back.

Some argue that Japanese knotweed is no more dangerous to structures than having a tree or shrub growing next to a property.

What to do if you have Japanese Knotweed

The first step to tackling the plant is to commission a professional Japanese Knotweed survey and find out the extent of the infestation. They will be able to tell you where it originated, and the best way to tackle it.

Professional treatment should then be organised, which usually involves the use of herbicide for excavation of the infestation.

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