It’s seen as a scourge by many, causing a headache for homeowners and often affecting house prices.
But Japanese knotweed isn’t any more of a threat than other “disruptive plants and trees” that don’t cause the same issues when it comes to property sales, a new study has found.
The report from Parliament’s Science and Technology Committee found that the UK has taken an “overly cautious” approach to the plant and there should be changes to the rules surrounding it.
Japanese knotweed was introduced to the UK in the 19th century and can be difficult to get rid of. Previously the plant has been believed to pose a risk of damage to buildings that are within seven metres of the above-ground portions of the plant – the so-called ‘seven metre rule’ – because of its underground shoots.
Mortgage lenders often require evidence that a treatment programme is in place to control Japanese knotweed which leads to added expense and headache for sellers.
But the Science and Technology Committee’s report said the latest research suggests that fears of physical damage to property from the plant are often overblown, particularly in comparison to other plants.
It said while it may be right to include information on the plant on a Seller’s Property Information Form, it should not have the significance it has when it comes to mortgage lending decisions.
“A significant industry is built around controlling Japanese knotweed,” the report says, “but we were told that mortgage lenders in other countries do not treat the plant with the same degree of caution.
“This gives us reason to believe that the UK has taken an overly cautious approach to this plant, and that a more measured and evidence-based approach is needed to ensure that the impact is proportionate to the physical effects of the plant in the built environment.”
It said the seven-metre rule is being used as a “blunt instrument” in some mortgage lending decisions and doesn’t reflect the latest scientific evidence.
The committee recommended that Defra commissions a study of international approaches to Japanese knotweed in the context of property sales to get more information on the issue.