Superweed October 21, 2019

Japanese knotweed is the poster child for invasive weeds in the UK. The tabloids and clickbait news will feed off any report, study or scare story. It is the scourge of property buyers and vendors, with mortgage lenders and surveyors flagging it as a serious issue and the government’s Science and Technology Committee has recently undertaken an inquiry into Japanese knotweed – although the report was somewhat inconclusive, and in my opinion, doesn’t fully seem to take on board the reasons why Japanese knotweed is such a problem.

The Committee quite rightly highlighted that Japanese knotweed is not particularly more damaging to buildings than other plant species – and in fact is somewhat less damaging than trees like sycamore. However, in my opinion, this fact was given excessive weight within the Committee’s lines of questioning and its report.

One point which was well-made to the Committee in response to their question of whether surveyors are under-valuing properties was that it is the market which values properties, and surveyors whose valuation should reflect the market.

If you were offered a choice of a house with Japanese knotweed, or an identical house which did not have a Japanese knotweed problem, you would choose the one without the problem – or there would be a significant difference in the price you were willing to pay, as a reflection of the cost of remediation and loss of use of those areas of your property that were affected, over the course of the treatment.

This loss of “usability” or “amenity” in the property is one reason why Japanese knotweed causes more problems than other plants. This impact on your “quiet enjoyment” of the property exists in potentia in any property where Japanese knotweed is close to the boundaries – which is also highlighted in many survey reports.

One of the other main reasons Japanese knotweed is a problem (which was highlighted to the Committee) is how difficult it is to control. Treatments can last up to five years (as opposed to a day for most works to remove a single tree); contaminated areas should be segregated and what’s more, they are likely to lose other plant species within the area, requiring re-planting to prevent further infestation by undesirable plant species. The whole process is time consuming and expensive.

So, while the fact that it can cause damage, spread quickly and easily and impact on the enjoyment of a property, Japanese knotweed is a problem principally because it is effectively the superbug of the plant world.

Staphylococcus aureus is a commonly-found bacterium, present on the skin and in the nose and throat. A large proportion of us (as many at one in every three people) carry this bug at any time, usually without any ill effects. Occasionally, this bacterium affects humans, causing infections of the skin, infecting cuts or wounds or occasionally causing food poisoning.

While it can cause problems, these problems are generally dealt with quickly by a course of antibiotics, and the problem is gone. This is analogous to something like our sycamore tree – where if a it is causing a problem on your land, you get in a tree surgeon and the problem can be quickly removed at relatively small cost.

However, some forms of Staphylococcus aureus have developed antibiotic resistance – particularly the well-known “superbug” MRSA. When MRSA causes an infection, it often doesn’t go away, even when antibiotics are used. MRSA requires targeted treatment, with “antibiotics of last resort” which can have more negative side-effects, can require hospital admission and unfortunately delay in treatment can, in some cases, result in the need for amputation of the affected area.

Japanese knotweed is to other plants what MRSA is to Staphylococcus aureus – it is a superweed. When you get an infestation, it needs to be managed promptly and properly by a professional in order to minimise the risk of damage and disruption. Although remediation is normally possible, it’s more expensive, long-winded and restrictive than getting rid of any other plant and it’s likely to significantly inconvenience you in the long term.

Talk to us about how we can help.

Chris Oliver
Operations Manager, Japanese Knotweed Solutions Ltd