As the UK's most invasive plant, Japanese knotweed is harmful to all who cross it.

Japanese knotweed usually emerges in March or April and grows rapidly to reach up to 2.5 metres in height by mid-summer, shading out native fauna which struggles to grow as a result. 

Identifiable by its hard, bamboo-like canes and distinctive shield-shaped bright green leaves, the knotweed does not produce seeds and instead is spread through accidental movement by foot or water. 

Eastern Daily Press: Japanese is an invasive plant species that is non-native to the UKJapanese is an invasive plant species that is non-native to the UK (Image: PA)

Invasive plant specialist Environet has looked at data from its live tracker to reveal that there are 769 known infestations across Norfolk, equal to one occurrence every 10 square kilometres. 

The majority of the plant can be found in and around Norwich, which has more than 70 such occurrences within its four-kilometre limits.

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But tackling its spread costs the UK nearly £250 million a year, according to Environet, with homeowners most at risk of damage. 

The group estimates that around 5pc of homes across the UK are affected by Japanese knotweed which can impact property prices by up to five or 10pc.

Eastern Daily Press: Environet's live heat map shows the areas of Norfolk most at risk of Japanese knotweed invasionEnvironet's live heat map shows the areas of Norfolk most at risk of Japanese knotweed invasion (Image: Environet)

Norfolk, with its myriad waterways and length of coastline, fares worse than those counties to the west and south, with 174 known infestations across Suffolk and 201 in Cambridgeshire.

Nic Seal, founder of Environet, said: "Vigilance is the best way to protect your property from the risks posed by Japanese knotweed.

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"Knotweed is easily identifiable during summer, but as we head through the autumn and into winter, the above-ground growth dies back and it becomes much harder to spot.

"It's also easier to conceal, so anyone viewing a property to buy should be extra careful.

"There are lots of horror stories out there but with professional help, knotweed can be successfully treated and a property's value can be largely restored."