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Home > News > When the law impacts gardening: knowing the rules on Japanese Knotweed

When the law impacts gardening: knowing the rules on Japanese Knotweed

01 June 2017 | Julian Pyrke

Japanese Knotweed (Fallopia japonica), although not native to the UK, has spread like wildfire following its introduction to the UK by the Victorians around 1886 as an ornamental plant.  In fact, it has thrived as a result of the warm, wet UK climate and also as a result of its isolation from Asian grazers and infectious organisms prevalent on that continent.

Despite the fact that its many produced seeds are ineffective in this country, it has a complex system of rhizomes below ground which make up 50% of the plant’s biomass (think icebergs!).  This enables the plant to propagate extremely efficiently no matter how you attempt to disturb it – for instance, it is possible for tyre tracks of a removal truck to inadvertently distribute small fragments of the plant which have been known to produce a new thriving plant as a result.

This would be of little concern save for the fact that the species directly competes with indigenous species, and can also penetrate and cause significant damage to any buildings on the land whether already present or about to be built.  Consequently, the Wildlife and Countryside Act 1981 has made it an offence to cause the spread of the plant – although it is not against the law to specifically having it on your land.  After all, natural causes can be responsible for its spread.

In recent years, it has been built into the national conveyancing protocol for both residential and commercial property practitioners that a seller disclose whether the property is affected by Japanese Knotweed and that being the case, whether a management programme is in place.  Many a buyer and/or mortgagee would be put off by this.

It is Complete Weed Control’s argument that should you find your dream property, you should not be put off by this, given the right type of management regime.  An investigative report costs around £450 to identify the presence and extent of the weed and to pave the way forward.  Often a 5-year programme can be satisfactory but it is difficult to completely eradicate the plant.  It merely has to be controlled. 

Considerations include the season of the year and the type of herbicide used, especially in relation to neighbouring land use and the presence of a water course.  Recent controlled experiments over a large expanse of land in South Wales has certainly proved that there is a long way to go before discovering total eradication techniques, but it is Complete Weed Control’s belief that many operators claiming to be able to do so, would struggle to evidence its success in the long term.  The findings have yet to be published but suffice to say, even covering a large expanse of formerly occupied land with impenetrable plastic sheeting has proved unsuccessful; the plant simply appears at the fringes and establishes itself as a new crop.

On a lighter note, Knotweed is known to produce a tasty meal and as such, you may wish to try out the Knotweed crumble recipe** formerly published in Environment Industry Magazine:

  • Cut 30 lengths of knotweed into 5cm chunks, place in an oven proof dish and pour over 4 tablespoons of orange juice and add up a mashed banana into the gaps. 
  • Separately mix in a teaspoon of powdered ginger together with 120g butter, 120g soft brown sugar and 180g flow, and sprinkle all of this over the top with your fingers. 
  • Place in preheated oven* at 180 degrees Celsius and cook for 20 minutes or until the crumble has turned golden.

For more information about this topic, get in touch with our Commercial Property team on 0117 906 9400 or

This article is based on a Seminar by Advanced Invasives and Complete Weed Contol in 2017. Any errors or misinterpretations of this seminar are unintentional.

However those wishing to bake a knotweed crumble faces a some practical challenges:

*Under the Environmental Protection Act 1990 is a controlled waste so can’t be taken off site without correct disposal procedures.  You will need to bake it where you found it.

**It is quite possible that the knotweed will have been subject to herbicide treatment – in which case do not eat!

The contents of this article are intended for general information purposes only and shall not be deemed to be, or constitute legal advice. We cannot accept responsibility for any loss as a result of acts or omissions taken in respect of this article.

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