Revealed! The harmless plants being mistaken for Japanese knotweed

Harmless garden weeds such as bindweed and ivy are frequently being confused with the highly invasive Japanese knotweed, research suggests. 

This could potentially scupper property sales unnecessarily.

Analysis of 2024 data from Environet’s Free ID Service, which invites members of the public to send in a photo of any suspicious plants in their garden for expert identification, shows that knotweed is correctly identified in just over a quarter – or 27% – of cases.

However, the general public’s ID skills have improved, up from just 16% who correctly identified knotweed in 2023.

Bindweed was the plant most commonly mistaken for knotweed, accounting for 12% of all photos sent into the ID service. It shares several characteristics with knotweed, including rapid growth, bright green heart-shaped leaves and white flowers, but unlike knotweed which is self-supporting, bindweed needs to wrap itself around other plants, walls or structures. Whilst bindweed is a nuisance for gardeners and can be difficult to eradicate, it doesn’t cause damage to property.

Dogwood, a woody shrub with bright red stems similar to knotweed’s, accounted for 5% of the nearly 500 photos sent in. Other plants commonly mistaken for Japanese knotweed include houttuynia, ivy, bamboo – which is also highly invasive – dock, lilac, bramble and honeysuckle. In early spring, Environet also sees a surge in photos of peony being submitted by worried homeowners, due to its red asparagus-like shoots which look very similar to knotweed when they first emerge from the ground.

Failure to identify and treat Japanese knotweed as soon as it appears will allow it to spread and quickly become established. Knotweed grows rapidly – at up to 10cm per day by early summer – to reach up to 3 metres in height. It can push up through paths, patios and driveways and over time can damage homes and outbuildings if left untreated. Knotweed can also spread across boundaries into adjacent properties, causing legal disputes between neighbours.

Emily Grant, director of Environet, said:

“We expect to see Japanese knotweed shoots emerge in warmer parts of the country and sheltered urban areas in late February or early March, so it’s important that homeowners and gardeners brush up on their ID skills and know what to look out for.

“The sooner knotweed is spotted, the sooner it can be professionally treated or removed, preventing damage and the risk of a legal case if it encroaches next door. Knotweed will still have to be declared to future buyers when the property is sold, but dealing with it quickly, before it has the chance to spread, is the best way to keep removal costs as low as possible and protect the value of your house.” 

Anyone who is unsure whether a plant in their garden is knotweed, can send a photograph for free identification to [email protected] in return for a voluntary charity donation.

Kindly shared by Estate Agent Today Picture courtesy of Adobe