Senior figures from the Japanese knotweed remediation industry have called for greater transparency as the UK enters "epidemic" risk levels.
The invasive plant, whose rapid growth can destroy man-made and natural structures in its path, threatens billions of pounds' worth of property transactions every year, and many professionals risk lawsuits as well as lost business.
Japanese Knotweed Control, one of the UK's first specialist remediation companies and a founder member of the Invasive Non-Native Specialists Association (INNSA), is leading a campaign to combat misinformation and to introduce a higher-level national standard for the management of the destructive weed.
David Layland, founder and managing director, explains: "We're embarking on a public communications campaign that we've nicknamed 'Gone But Not Forgotten', because one of the biggest challenges, besides getting rid of the plant itself, is the amount of misinformation and misconceptions that exist in the UK."
"The biggest of these is the myth that once knotweed has been treated, the problem has gone away. In reality, without a proper warranty, insurance and long-term remediation strategy, your knotweed treatment can leave you just as much at risk as when you first spot the distinctive leaves."
When a herbicide is applied to the plant, it translocates around its extensive root system and stops plant cells from growing. Over time the plant just rots into the soil but until it has completely decomposed, small nodules of viable material may still be present. If the plant is left alone, herbicide is by far the least expensive and a highly effective treatment method.
However, another common problem is that the plant in fact stores nutrients in a maze of roots underground enabling it to hibernate during the winter months. The plant appears dead, but in fact is very much alive and if disturbed, will spread and cross contaminate providing a nasty surprise in the summer.
The UK's mild, wet winter coupled with this year's humid summer has encouraged the growth of the plant which can grow up to 40mm per day. It can take less than 0.7g of rhizome (subterranean stem) - no bigger than a fingernail - for an infestation to take hold, resisting domestic weed killers and growing through bricks, mortar and tarmac in its path.
As many as two thirds of UK mortgage brokers have reported that they have had transactions negatively affected by Japanese knotweed, with many forced to withdraw mortgage applications because of the presence of the invasive plant.
Japanese Knotweed Control is reassuring property owners, estate agents and conveyancers that the presence of knotweed on a property should not affect a sale provided the remediation strategy has the correct warranties and insurance.
David Layland continues, "If you have the right information and back-up from your knotweed professional, such as insurance and warranties, then you should have not only peace of mind but also the legal guarantee that solicitors and conveyancers are looking for to demonstrate the knotweed issue is under control."
Japanese Knotweed Control was the first company in the industry to offer an insurance-backed warranty on all its treatment options. All work undertaken is fully insured and underwritten by Lloyds of London specifically for the treatment of non-native plant species and carries professional indemnity cover for £5 million including structural damage cover.