Japanese knotweed Yorkshire: thousands of infestations of invasive plant in Sheffield, Rotherham, Doncaster, Barnsley and Huddersfield

There are almost 60,000 known occurances of Japanese knotweed in the UK, and more than 2,000 of those are right here in Yorkshire, with half of those in Sheffield and Rotherham.

Figures released by Environet in a document seen by this newspaper show that Japanese knotweed is most prevalent in Rotherham, with 543 instances known and recorded.

Sheffield has the second most infestations of Japanese knotweed with 517; Huddersfield 168, Doncaster 134 and Barnsley 118.

The company, which specialises in tackling invasive plant species, has created a Japanese knotweed heatmap which enables you to enter yours or any postcode to see what the risks are in the area you are interested in.

Tackling knotweed costs the UK economy an estimated £250 million a year and homeowners are one of the groups most at risk – not only from potential damage to their property, outbuildings and gardens, which can be costly to repair, but also from legal risks arising from encroachment or when properties are sold.

Is it illegal to have Japanese knotweed on my property?

No. It isn’t. However, if you do have Japanese knotweed growing on your land, and it crosses a boundary into an adjacent property, legal disputes can arise between neighbours. Similarly, when properties are sold, sellers are asked a direct question about whether knotweed is present, even if hidden beneath the ground or within 3 metres of the boundary, and those who fail to declare it can be sued by their buyer for misrepresentation. It is estimated that around five per cent of all homes in the UK will have Japanese knotweed.

What does Japanese knotweed look like? How to spot it…

Japanese knotweed usually emerges in March or April and grows rapidly to reach up to 2.5 metres in height by mid-summer. It is identifiable by its hard, bamboo-like canes and distinctive shield-shaped bright green leaves which grow in a zigzag pattern along the stem. Mature plants flower in August, becoming covered in clusters of delicate tasselled creamy-white flowers.

Knotweed does not produce viable seeds as all the plants in the UK are female, so it is usually spread accidentally through the movement of soil or gardening waste, or via rivers and streams when pieces of rhizome break off and take hold in new locations.

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

" Make sure you know what knotweed looks like and how it differs from other common garden weeds like ivy and bindweed, so you can keep an eye out for it in your garden and neighbourhood.”

" 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.”