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Tackling invasive plants species in the Lake District

PUBLISHED: 00:00 10 August 2017

A volunteer at Littledale Hall in north Lancashire tackling rhododendron

A volunteer at Littledale Hall in north Lancashire tackling rhododendron

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It’s over here and over grown – an invasive plant that could pose a major threat to the Lakes economy

National Trust team clearing pigmyweed from Derwentwater (Picture: Stuart Holmes)National Trust team clearing pigmyweed from Derwentwater (Picture: Stuart Holmes)

A dedicated army of Lake District volunteers are fighting a rearguard action against a formidable foe – alien invaders that can even wrap around the necks of unsuspecting swimmers.

The reality might not be quite as spectacular as a horror movie but the threat is far more real. In fact, some believe it poses a greater threat than climate change.

These aliens find their way into our lakes, along the riverbanks and across the countryside and they are, almost without exception, monsters of our own creation.

National Trust rangers and volunteers across the Lake District are now spending more than 350 days a year tackling the growing problem of non-native invasive plant species in the area.

Rangers in the Lakes clearing Himalayan Balsam  (Picture: Roland Wicksteed)Rangers in the Lakes clearing Himalayan Balsam (Picture: Roland Wicksteed)

And they could be fighting a losing battle unless everyone does their bit to halt their relentless march.

Some seem like quintessential Lakeland plants. These include the rhododendron. Its flowers might look the part but the several million seeds they produce each year see them dominating areas and making them immensely difficult to remove. National Trust rangers have been trying to repel them for more than 15 years in places like Windermere’s west shore, Monk Coniston and Wray Castle.

These thugs of the plant world prevent native flowers from growing and can impact on trees by damaging the surrounding habitat.

Their leaves and buds contain toxic chemicals that are indigestible to grazing animals and poisonous to humans and bees. ‘Rhody bashing’ - where the branches are cut down to the stump - is taking place to remove as many as possible over the coming weeks before the plants seed.

Spraying Rosa Rugosa, another invasive species from the Far East which is taking a gripSpraying Rosa Rugosa, another invasive species from the Far East which is taking a grip

Himalayan balsam is good for bees but not much else. If not kept in check, it threatens to destroy the area’s diverse natural habitats. Large scale bashing has to take place every three weeks in Langdale to stop seeds from setting and National Trust rangers work in partnership with South Cumbria Rivers Trust on regular bashes around Windermere, Langdale and Ullswater.

Japanese knotweed is a name to strike terror in the heart of any homeowner. But it has been in this region for some 90 years and its small pink flowers can be spotted in some of the area’s valued habitats including Sandscale Haws near Barrow-in-Furness where it spreads quickly and out-competes native species by preventing sunlight from reaching them. Rangers and volunteers have to cut, burn and treat the area each year to avoid re-growth.

One of the latest and most pernicious is Crassula helmsii, known as swamp stonecrop or New Zealand pigmyweed and the bad news is that it has set up home in Derwentwater.

According to Penny Webb, the Lakes countryside manager at the National Trust, it is almost impossible to eradicate and grows 200 times faster than native pond plants. ‘Aliens such as Crassula pose problems on a global scale, impacting on native species and threatening recreational income for locations such as the Lakes,’ she said.

Wild swimming could be a thing of the past in Derwentwater if weed takes control (Picture: Steve Barber)Wild swimming could be a thing of the past in Derwentwater if weed takes control (Picture: Steve Barber)

‘There is an argument to say it is a bigger threat to habitats than global warming. Despite this, it is not being flagged up by the Government. There needs to be a rise in awareness before it is too late.’

Crassula arrived in the UK from Australasia just before the First World War as a way of oxygenating aquariums. It has had the opposite effect, strangling the life out of water courses with thick matted areas that can be three metres deep.

Native plants are threatened, fish die due through a lack of oxygen in the lake and water sports such as swimming and boating become impossible as the lake becomes choked. There have even been reports of wild swimmers coming from the water with Crassula wrapped around their necks.

And it is so vigorous only takes a small piece to spread it to other lakes. So far, Buttermere, Crummock Water and Loweswater have remained clear and Penny and the team are involved in a public education exercise to make people aware of the need to clean canoes, wet suits, boots and dogs at the waterside before moving on to other locations.

The only option for volunteers is to cut and physically remove the Crassula by hand and this is helping to keep it from taking over. The wind has also helped, confining it mainly to the eastern side of Derwentwater although it has been spotted in the channel by Lord’s Island.

‘Doing nothing isn’t an option,’ said Penny. ‘If we ignore the problem it will spread to other lakes and the economic benefits the region gets from the lakes will be lost.’

Some research is going on around the country to find the best way to control this mean green machine but, for now, the visitors need to wash their kit and the region’s volunteers need to keep bashing and slashing for all they’re worth.

Anyone interested in finding out more about supporting the work of the National Trust in the Lake District should visit For more information on the South Cumbria Rivers Trust invasive plants summer work party dates, visit

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