Plant experts combat knotweed misidentification in bid to save millions in property sales

Invasive plant experts Japanese Knotweed Control are launching a campaign to educate property professionals on how to recognise Japanese knotweed throughout the seasons, in an attempt to combat misidentification and minimise the risk to property transactions.

The invasive plant threatens millions of pounds’ worth of property transactions in the UK. Recent research conducted by the Crop Protection Association (CPA) revealed that one in seven homeowners (15%) saw a property deal fall through due to a knotweed infestation, and one in five (20%) saw a drop in their house value because of the presence of the plant.1

As many as two-thirds of UK mortgage brokers have reported that Japanese knotweed has negatively impinged on transactions, with many forced to withdraw mortgage applications because of the presence of the invasive plant.2

Japanese Knotweed Control has released an infographic outlining the appearance and key characteristics of knotweed in each season, in a bid to help estate agents, conveyancers and surveyors identify the destructive plant.

Japanese knotweed, an invasive plant brought to England in the Victorian era, grows rapidly and has the potential to destroy man-made and natural structures in its path. It is able to grow through cracks in concrete and undermine the structural integrity of buildings.

Whilst there is a known Japanese knotweed infestation in every 10km2 of the British Isles, in many instances the plant is wrongly identified. At every stage of its life cycle, the plant can easily be confused with other species such as Himalayan balsam, bind weed, Russian vine and bamboo.

The CPA’s research showed the extent to which people are unable to identify the plant. Less than a third (30%) felt confident that they’d be able to recognise knotweed, one in six (17%) said they had a good understanding of the plant, while over one in four (27%) stated that they knew nothing at all about knotweed.

Japanese knotweed is at its most easily distinguishable stage in summer, when it develops an abundance of green leaves, distinctive white flower, and a green stem that resembles bamboo with purple speckles.

Throughout autumn, the leaves begin to wilt and brown, and in winter Japanese knotweed draws back into its rhizome whilst the canes lose colour and turn into woody stalks. The plant lies dormant in winter, but its lifeless appearance can falsely lead people to believe the plant has died. This often results in attempts to cut the plant back, which can cause rhizome fragments to spread and stimulates further growth.

David Layland, joint managing director of Japanese Knotweed Control, said: “It is so important that estate agents and surveyors know what knotweed looks like at each stage in the year, to avoid the risk of misidentification – the financial implications of which could be potentially catastrophic.”

“We were recently asked to conduct a survey on a property in Oldham, Greater Manchester, after the house was valued as worthless because of a suspected case of knotweed. The plant in question turned out to be Himalayan balsam, and the house went on to sell for the asking price of £130,000.”

In the case of uncertainty as to whether a plant is Japanese knotweed, estate agents are encouraged to consult a professional to gain a second opinion, before continuing with the transaction.

Layland went on to reassure property owners and estate agents that even if knotweed is present on the land, it does not necessarily need to affect a sale. He explained: “If a proper remediation strategy is in place with robust warranties and insurance, the property owner can have peace of mind that the legal guarantees can demonstrate to solicitors and conveyancers that the knotweed issue is under control.”


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