Japanese Knotweed - Not a weed to ignore!

Japanese Knotweed is a serious consideration for Lenders, Developers, Purchasers, Landowners, Planners and Surveyors. The impact of the discovery of Japanese Knotweed on land and buildings can prove to be significant.

Source: Charles Lyndon

Anyone who has a garden will be more than aware of the speed in which weeds will grow, which if left uncontrolled can become unsightly and overgrown very quickly. Having acquired an overgrown allotment a few years ago, which I spent many hours clearing and digging I can tell you with authority that weeds are almost impossible to eradicate and therefore need to be regularly controlled. Most varieties of weeds are harmless if regularly managed, with the exception of the odd thorny or irritant types of weeds. There is however one particular type of weed that has received increased publicity over recent years, due to the size and rate of growth. There are plenty of opinions in relation to the risk and the extent of damage that Japanese Knotweed can cause to buildings/structures and there are plenty of examples of people affected by it which has resulted in denial of mortgage applications, disputes with insurers and extensive costs in trying remove or control its growth. On the other side of the coin, recent research by AECOM challenges popular opinion and suggests ‘Japanese knotweed is no more of a threat to buildings than other plants’. The research of members of the Royal Institution of Chartered Surveyors (RICS) and the Property Care Association (PCA) who have interacted or dealt with Japanese Knotweed in one way or another found that ‘Only between 2% and 6% of respondents reported any co-occurrence of Japanese knotweed and structural damage to buildings. Our paper also concluded that where Japanese knotweed is associated with damage, it is likely that the plants will have exacerbated existing damage, rather than being the initial cause of the damage’. The results of the research are interesting and well worth a read; (Link).

Despite research by AECOM and others that suggest that Japanese is not the problem that the media would have us believe, we do live in a risk averse society. To those who buy/sell/rent and generally live in property I suspect that they will be un-swayed in their opinion and instead choose to panic at the mere mention of the words Japanese Knotweed in a similar way to which many people react to the words ‘Asbestos’ or ‘Subsidence’ etc. For those involved with property surveys and inspections it is essential to be able to identify Japanese Knotweed and to be able provide appropriate advice. This article is therefore written to provide some basic information about Japanese knotweed which can be used to supplement further reading.

Japanese Knotweed (Latin name - Fallopia japonica) was introduced into the UK as an ornamental plant by the Victorians. It originated from Asia in countries such as Northern China and Japan where it grew in harsh habitats on the slopes around volcanoes. When introduced into the UK the conditions were far more fertile than those in Asia allowing the plant to thrive. Japanese Knotweed is a Perennial Plant, meaning that it will grow for many seasons with the plant dying back in the winter and re-growing the following spring. Japanese Knotweed is capable of growing 10cm per day and it is highly invasive and capable of exposing weaknesses in buildings, foundations, concrete and tarmac. It has the capability of regenerating from minute rhizomes (a root or creeping stem), therefore there is a significant risk of spreading the plant from digging and other disturbance. Effective removal of Japanese Knotweed therefore requires a specialist, which as you would expect can be expensive.

As stated previously, Japanese Knotweed is a serious consideration for Lenders, Developers, Purchasers, Landowners, Planners and Surveyors. The impact of the discovery of Japanese Knotweed on land and buildings can prove to be significant. Land values can be reduced to take into account remediation works. It is therefore worth knowing how to identify Japanese Knotweed to firstly establish its presence and if identified how to deal with it. Devon County Council provided an excellent guide to the identification of Japanese Knotweed which is summarised below. The original link to the article is no longer active however the images and information below are still relevant:

How to identify Japanese Knotweed

  A Typical Japanese Knotweed Leaf

In the early spring red/purple shoots appear from the ground and grow rapidly forming canes. As the canes grow the leaves gradually open and turn green:

The plants are fully grown by early summer and mature canes are hollow with a distinctive purple speckle and form dense stands up to 3 metres high:

The plant flowers in late summer and these consist of clusters of spiky stems covered in tiny creamy-white flowers:

During the late autumn/winter the leaves fall and the canes die and turn brown. The canes remain standing throughout the winter and can often still be seen in new stands in the following spring and summer:

The rhizome is the underground part of the plant. It is knotty with a leathery dark brown bark and when fresh snaps like a carrot.  Under the bark it is orange or yellow.  Inside the rhizome is a dark orange/brown central core or sometimes it is hollow with an orange, yellow or creamy outer ring, although this is variable:

Japanese Knotweed and the Law

In 2016, the Environment Agency withdrew its Japanese Knotweed Code of Practice due to new government guidelines. This was replaced in March 2017, by the Invasive Non-Native Specialists Association (INNSA) new Code of Practice. Access to the new code is not as straightforward as the EA Code however you can request a copy from the following: (Link)

Below is a summary of the raft of legislation that relates to Japanese Knotweed which is taken from the Environment Agency’s Japanese Knotweed original Code of Practice.
  
Japanese Knotweed is classified as controlled waste and its disposal is strictly regulated. For example soil containing Japanese Knotweed roots/rhizomes is classified as contaminated waste and can only be taken to a licensed landfill site. Failure to dispose of Japanese Knotweed appropriately may lead to prosecution under section 34 of the Environmental Protection Act (EPA) 1990.  Also, although it is not a criminal offence to have Japanese Knotweed on your land, allowing it to grow onto neighbouring land may constitute a nuisance and as such may provide grounds for a civil action from those affected.

Other relevant legislation includes Section 14(2) of the Wildlife and Countryside Act 1981 states that '…if any person plants or otherwise causes to grow in the wild any plant which is included in Part II of Schedule 9, he shall be guilty of an offence'. Japanese knotweed is one of the plants listed in Schedule 9. Also, waste must be transferred to an authorised person, in other words a person who is either a registered carrier or exempted from registration by the Waste (England and Wales) Regulations 2011. A waste transfer note must be completed and signed giving a written description of the waste as per regulation 35 of the Waste Regulations. The Hazardous Waste Regulations 2005 contain provisions about the handling and movement of hazardous waste.

Japanese Knotweed continues to receive an increased amount of negative publicity which makes it increasingly important for those undertaking property surveys and inspections and giving property advice to be able to identify its presence and give appropriate and proportionate advice.  This article should serve as a good starting point and hopefully generate interest for further reading and research for built environment and related professions. 

Author: Gary O’Neill

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