Invasive non-native plants: are we winning the battle?

January 10, 2018


Last year was a busy year for the River Dee Trust and the River Don Trust and their army of volunteers in the fight against invasive non-native plants on our riverbanks. On the banks of the Dee, Himalayan balsam is the biggest invader – the swathes of bright pink flowers look cheerful enough, but they quickly get out of hand with flowers that explode seeds everywhere. Our survey at the start of the year identified over 40 hectares of this plant along the riverbank. 


The river banks also have the invasive Japanese knotweed, which is reputedly hard-to-kill with roots that break through concrete, and giant hogweed, whose sap causes severe burns on contact with skin. 

On the banks of the Dee, from Drumoak to Aberdeen, these plants have taken hold and over the last few years the Trust has been making efforts to combat them. For the last three years, Offset Mitigation funding from the Aberdeen Western Peripheral Route project, has enabled us to ramp up the pressure in our efforts to control the plants.
So, are we winning the battle? Well, at this stage we are optimistic. We’ve had a lot of support from volunteers over the last three years, helping to locate plants, spraying them with herbicide or pulling them out of the ground. In 2017 our surveys showed that Japanese knotweed now covers only 10% of the area it did in 2015, thanks to continual spraying with herbicide. 

The amount of giant hogweed and Himalayan balsam on Deeside has increased compared to 2015, but this is due to the effect of Storm Frank, which spread their seeds far and wide. Where we apply treatment, we have found a significant reduction in these plants – even in one year - showing that control is possible. 
Giant hogweed has has now overrun many of the river banks on Donside. It is unmistakable when full-grown, reaching up to 5 metres tall. The sap of the plant is toxic and causes severe burns, and so the plant should be avoided.
Targeted action to control these plants has been taken since 2017 with Offset Mitigation funding from the Aberdeen Western Peripheral Route project.  With the help of trained volunteers, over 20 hectares of giant hogweed was killed, on the Don and Urie, with herbicide in 2017. Plants are individually sprayed, to avoid harming any other plants. However, not all areas could be treated in 2017 and with seeds having been spread for many years, this is only the start of the work.  

So, we think we can win! But we still have a way to go yet. Our teams of volunteers – which included companies such as Aberdeen Asset Management, BP, Costain Upstream and Scottish Hydro Electric, who carried out corporate work days with the River Dee Trust, helped to remove nearly 14 of the 40 hectares of the Himalayan balsam in 2017, and all the Japanese knotweed and giant hogweed (1 hectare) on the Dee were also treated last year.

A big thank you is owed to all the volunteers who took pride in their local river and helped control this plant over the last year. And for anyone wondering what to get involved in this year (April – September), please consider volunteering with the River Dee and River Don Trusts. 

Further support for this work can be given through the Tesco Bags of Help Grant Scheme at Tesco in Banchory and Inverurie. Customers can use their tokens to vote for the Dee (Banchory) and Don (Inverurie) Invasive Plant Project throughout January and February, which could provide a cash boost to this work of up to £4,000 on each river.

A North East Invasive Non-Native Species Forum is being set up to address invasive animals and plants, such as giant hogweed, to enable communities throughout Aberdeenshire to actively tackle these problem species in their areas. The Forum will meet on 28th February at The Kintore Arms Hotel, and anyone who would like further details should contact calum@riverdee.org


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Tackling Non Native Invasives

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Tackling invasive non-native plants along the banks of the River Dee – such as Japanese knotweed, giant hogweed, Himalayan balsam and North American skunk cabbage - has become a priority for the River Office because of their potential impact on our river and its existing, native species.

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