THE infamous Japanese knotweed is well-known for being Britain's most invasive plant and there are more than 100 infestations across Cornwall.

Japanese knotweed has a bad name amongst horticulturists and homeowners alike as the incredibly invasive plant can damage property and land beyond recognition. 

The zombie-like plant can grow a whopping 10cm a day between May and July, causing thousands of pounds worth of damage.

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The government estimates it would cost £1.5 billion to clear the UK of knotweed and homeowners who fail to stop the spread of the plant on their land can face fines and even jail time under ASBO legislation. 

Falmouth Packet: Japanese knotweed heat map of hot spots in Cornwall.Japanese knotweed heat map of hot spots in Cornwall.

As the UK’s most invasive plant enters its spring growth phase, Japanese knotweed expert Environet reveals the latest hotspots using data from its interactive online tracker, Exposed: the Japanese Knotweed Heatmap.

Populated with more than 55,500 known infestations of Japanese knotweed, charting the spread of the plant across the UK, Exposed informs homeowners and potential homebuyers of the local presence of knotweed and the potential risk to their property.

Users can enter a postcode to discover the number of reported knotweed sightings nearby, with hotspots highlighted in yellow or red.

The Cornwall Japanese knotweed hotspots for 2022 are: Falmouth with 31 infestations in a 4km radius, Camborne (46), St Austell (32), St Blazey (42) and Bodmin (22).

How to spot a Japanese knotweed infestation:

Following its winter hibernation, knotweed begins to grow in March or April, depending on the local ground temperature, reaching up to 3 metres in height by mid-summer.

Homeowners spending more time in their gardens this spring may notice purple or red asparagus-like shoots now emerging from the ground and quickly growing into lush green shrubs with heart or shovel-shaped leaves and pink-flecked stems.

What effect does it have on your property?

Pushing up through cracks in concrete, driveways, patios, paths, drains and even the cavity walls of our homes, Japanese knotweed can reduce a property’s value by 10 per-cent and make it difficult to sell, unless a professional treatment plan is in place with an insurance-backed guarantee to satisfy mortgage lenders.

According to Environet’s research, approximately 5 per-cent of homes are currently affected, either directly or indirectly (neighbouring an affected property), knocking around £20 billion off UK house prices.

To view Japanese knotweed infestations in your area or to report a sighting, visit: