Speed is key to avoid tying yourself in knots over knotweed

22 June, 2017
by: Cripps Pemberton Greenish

With summer approaching, the nation will soon be in bloom again. However there is one perennial, introduced in Victorian times as an ornamental plant, which you will certainly not want to find growing on your land.


Japanese knotweed is a fast growing plant with a bamboo like stem from which grow lush green leaves and small white flowers that bloom in September and October. It is one of the fastest growing plants known – indeed it can grow by up to 10 cm in a day and fast takes over from other plants.


So how do you get rid of it?
Easier said than done. Knotweed is very difficult to eradicate. Rhizome segments can remain dormant for up to 20 years so when the plant is superficially cleared from areas it is possible for it to remain, only to cause problems in later years. As a result, knotweed can only be removed by licensed contractors who dispose of it in designated land fill sites. It constitutes controlled waste under the Environmental Protection Act 1990. Smaller outbreaks of knotweed in gardens can be treated with herbicides but treatment can take a few years to be effective.


What’s all the fuss about?
In the countryside, knotweed takes over the habitat of native species damaging the local ecological balance. This resulted in the Wildlife and Countryside Act 1981 making it an offence to plant Japanese knotweed. This Act imposes a duty on land owners to control knotweed – although that duty does not extend to eradicating it. Therefore, given its ability to spread, knotweed can pose a real threat to the values of adjoining land.


However, its effect on nearby buildings is one with which the property industry is most concerned. The spreading roots of Japanese knotweed can cause structural damage to buildings. Because it is difficult to eradicate completely there is a threat of further damage. As a result, mortgage lenders are reluctant to lend on properties which have had a history of damage from knotweed. In fact, some lenders have reportedly refused to lend on properties where valuers have seen knotweed in the garden or nearby land.


This, in turn, has led the Law Society to consider the issue. The Law Society Property Information Form (TA6) contains a question about the presence of Japanese knotweed on land.


It will be up to valuers to identify knotweed in order to report on risk. It is not always easy to identify. In the winter months just bare stems are visible. New stems are a reddish purple in colour and can be seen emerging from what appear to the untrained eye to be dead stems. Valuers will need to be trained to correctly identify knotweed and then accurately report the risk to lenders.


In 2015, the Royal Institute of Chartered Surveyors (RICS), produced a paper on Japanese knotweed – identifying it, assessing the risk and advising on management and eradication. It also sought to reduce overreaction to it. The RICS points out that, whilst Japanese knotweed can pose problems for buildings, it is more of a risk to outbuildings, boundary walls and conservatories.


We have found some knotweed on our land – what do we do?
Management plans to control and eradicate Japanese knotweed can be implemented by specialist contractors with guarantees being offered to provide reassurance to house owners. However, it should be noted that often guarantees are only provided once several treatments have taken place over a few years. That means that a property blighted by Japanese knotweed can prove difficult to market even though expensive eradication treatment has already taken place.


Whilst Japanese knotweed on one’s own land can be tackled directly, it is rather different where Japanese knotweed is growing on adjoining land. As it is a pest, there is a duty on a land owner not to allow it to spread. But it is so widespread in some of London’s parks that total eradication seems nigh impossible. The threat of invasion is omnipresent.


Property owners should consider tackling outbreaks of Japanese knotweed without delay and should also insist that their neighbours do so where it is growing on adjoining land and could spread. With the lending market still restricted, property owners risk their properties becoming unmortgageable and therefore unmarketable due to the presence of Japanese knotweed. Effective eradication will remove not just the pest, but will enable owners to provide a positive response when a buyer’s solicitor requires disclosure.