Tackling the knotty issue of non native invasive weeds: what impact will Brexit have?

| 21st September 2016
Ecologists want the EU's new List of Alien Species of Union Concern regulations kept when Brexit is triggered

As leading figures from the world of law, ecology and technology prepare to come together and discuss how best to deal with non-native invasive plants in the UK, more research is still needed on how best to manage these species taking over the countryside writes LAURA BRIGGS
Setting out a clear framework on how to deal with high-risk species, new regulations give a clear large scale approach, but there are worries that in light of Brexit, regulations which deal with these destructive weeds may be taken away

The Property Care Association's (PCA) second annual Invasive Weed Conference entitled ‘Risk, Roots and Research' takes place on November 22 and will include talks on the problems of Japanese Knotweed, aquatic invasive plants, and biocontrol and physiochemical control optimisation.

Professor Max Wade, Chairman of the PCA's Invasive Weed Control Group, said: "A lack of information is one of the biggest obstacles to achieving the effective management of Japanese knotweed and other non-native invasive plants in the UK. 

"Our intention is to offer a level-headed and evidence-based approach to tackling the issue and create a platform for delegates to access a wide-range of expertise from high calibre, informed sources."

The fight against non-native species made great strides forward recently when the List of Alien Species of Union Concern finally came into force on August 3, 2016, as part of new EU-wide regulations.

Setting out a clear framework on how to deal with high risk species, the new regulations give a clear large scale approach, but there are worries that in light of Brexit, regulations which deal with these destructive weeds may be taken away.

Dr Mark Fennell, Principal Ecologist at AECOM says: "It is important that this new EU Regulation along with the many other EU-based regulations relevant to UK environments be retained moving forward."

One of the most well-known non-native invasive weeds is Japanese Knotweed (Fallopia Japonica) which can grow to around two metres tall and was introduced to the UK in 1825. It has been growing ferociously across the UK landscape since 1886.

Both Prof. Wade and Dr Fennell recognise a real need to establish evidence-based risk assessments for this species, so informed decisions can be made on the threat Japanese Knotweed poses to buildings and other structures. 

The role of the Royal Institution of Chartered Surveyors (RICS) in providing surveyors with appropriate guidance is welcomed by professionals and academics, as is the code of practice, training and certification available through the Property Care Association, for those managing companies and working to control this plant.

It took 130 years for Japanese Knotweed to reach its peak, but the likes of Floating Pennywort took just 20 - this plant arrived on UK soil in the 1980s and was first recorded in the wild in 1990. Floating Pennywort is racing to the top of the list of weeds to watch out for, as it spreads at a staggering rate throughout waterbodies and river systems. The species was banned for sale in 2012 but fears are that this is too little, too late. The species is now well established in many waterways, particularly around London and Manchester, and over the last few years has begun to overrun the Ely Ouse and the Cam in Cambridgeshire where extensive and costly control programmes are underway, made more difficult by a limited selection of chemical controls suitable for aquatic plants. Floating Pennywort can form dense mats, has major ecological impacts and restricts water flow.

Dr Fennell said: "There is an urgent need to keep an eye on the horizon for what might be heading in our direction.  One to watch out for, handkerchief in hand, is Ragweed (Artemisia Artemisiifolia), known from the wild in the UK since 1836.  This plant produces pollen which can cause serious hay fever to the extent that it is considered a serious weed in parts of North America and increasingly so in Europe."

He said the fear is that there is a trigger which will enable Ragweed to spread just as Japanese Knotweed has. Ragweed is a medium-sized perennial herb reaching up to one metre, with its seeds spread by attaching to fur and clothes.

Another nuisance weed of waterways, parks and farms is Giant Hogweed (Heracleum Mantegazzianum). If the toxic sap of this species gets on your skin, it can result in severe blistering, long-term scarring and sensitivity to sunlight.

This massive and impressive plant, once a favourite in Victorian ornamental gardens is really beginning to make itself known as more injuries from the plant are reported. It's especially important to alert children to the dangers of this plant, as often they are fascinated by its sheer size.

To date, two of the most significant recent achievements in the fight against non-native invasive plants are the revision of the Invasive Strategy for Great Britain, and the emergence of a trade association for invasive weed control companies.  The GB Strategy is the UK Government's blueprint for dealing with invasive non-native species and highlights the importance of teaming preventative measures with the ability to mount a rapid response to potentially invasive species.

Prof Wade said: "This strategy has received input from across a range of stakeholders and is fit for the years to come. The Property Care Association has raised the standard of practice in this industry through introducing standards and training, ensuring that the millions of pounds spent on the control of invasive non-native weeds is well spent. 

"This development is particularly timely now that government agencies in England do not provide guidance, as exemplified by the removal of the Environment Agency's widely consulted Knotweed Code of Practice (now on the NNSS website). 

"The PCA has been filling part of this gap for invasive weeds.  As a member of the Non-Native Species England Working Group, the PCA needs to sustain its support of the GB Strategy, and why not build on its success by taking on the mantle of invasive non-native pests, and bring a more coordinated approach to the likes of Asiatic Clams, Asian Hornet and Asian Tiger Mosquito to the table nationally?"

Identification of plants and other invasive non-native species is covered by the Field Guide to Invasive Plants and Animals on Britain and the identification sheets on the NNSS's website.

  • The trade body PCA has existed for more than 85 years and represents a number of UK structural bodies, including flood protecting and invasive weed control industries.


  • The Invasive Weed Control Group was set up in 2012 by the PCA together with the Royal Institute of Chartered Surveyors (RICS) and invasive weed control companies operating within the UK.


Laura Briggs is the Ecologist's UK-based news reporter

Follow her here: @WordsbyBriggs






Help us keep The Ecologist working for the planet

The Ecologist website is a free service, published by The Resurgence Trust, a UK-based educational charity. We work hard - with a small budget and tiny editorial team - to bring you the wide-ranging, independent journalism we know you value and enjoy, but we need your help. Please make a donation to support The Ecologist platform. Thank you!

Donate to us here