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Eradicating Japanese Knotweed from the Dolgellau area

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15 September 2016

Within the next few weeks, Snowdonia National Park Authority officers will proceed to control the invasive and destructive plant, Japanese knotweed, in the Dolgellau area.

Thanks to a grant from Natural Resources Wales, the Authority and its partners namely Prince Albert and Dolgellau Angling Associations, Dolgellau Rotary Club together with local contractors, will attempt to control one of the country’s most destructive plant.

During the mid-nineteenth century, the Japanese knotweed (Japonica var japonica) was introduced to Britain as an ornamental plant for the garden and since then it has spread rapidly, particularly along watercourses, transport routes and areas of wasteland. It falls into the same family as the dock leaf, but is a tall and vigorous plant with branching stems covered with purple spots. Between August and October it will produce clusters of small cream flowers and as it is a perennial rhizomatous plant (plant with stems growing underground), the underground stems can grow between two and seven meters and the above ground stems can grow up to between two to three meters.

It is now an expert at invading natural habitats, depriving wildlife of migration routes and depriving rivers, hedges, railroads and road verges of indigenous plants. It can also damage buildings and hard surfaces and once it has established itself under or around buildings, it is very difficult to remove it. It can also cause damage the flood defence structures and due to its tall stems it create visibility problems for walkers on footpaths.

Gethin Davies, the Authority’s ecosystems and Climate Change Officer said,
"Removing this invasive and destructive plant is difficult and exhausting work and unfortunately, using a strimmer to cut it down is not the answer. It would be much better if it’s left as it is before treating it with herbicide or you can dig it all up, including the roots, and leave it to dry before burning it. In Dolgellau, we will be spraying it with herbicide and with the help of our partners, along with the information about infected areas which have been recorded on our website and app, it is possible for us to progress with the work."

Natural Resources Wales officer, David Smith from said,  
“This project gives a real opportunity to eradicate this invasive species on a catchment scale, coordinating a systematic programme of survey and works. It will also work with local communities, landowners, anglers and interest groups, to guide, enthuse and enable those who know these rivers best, to help tackle this threat to our riverine ecology and special protected wildlife sites. Such local community input will help create long-term, sustainable strategies to protect our rivers from these pernicious threats.”

The National Park’s partners in the project, namely the local angling associations have already been very active removing the invasive plant. John Eardley from the Prince Albert Angling Society said,
"We have been treating Japanese Knotweed on the banks of the Mawddach and Wnion in the Llanelltyd area for 3 years. Although we have been very successful in reducing some extremely large stands, it is difficult to completely kill the root system and ongoing treatment is essential. It is also vital to accurately map locations as the plants are easily hidden by other vegetation as size decreases in the years following treatment. It is also important to be vigilant for new material which has broken off from areas upstream and has been transported downriver during flood conditions.”

Gavin Jones, Secretary of the Dolgellau Angling association added,
"Dolgellau Angling Association was pleased to be able to contribute towards the grant application from Natural Resource Wales to tackle this invasive and destructive plant from our river banks.
This grant has enabled DAA volunteers to be up skilled and provided the tools to help eradicate this plant that has damaged and closed off access to our waters.
DAA look forward to working closely with our partners on a project that will improve our environment, angling and the tourism this brings."

If people know of areas in Dolgellau where the Japanese knotweed is growing but has not been recorded, it is possible to record the locations on http://eryri.atlas.cofnod.org.uk. For more details on Japanese Knotweed, visit www.eryri-npa.gov.uk/ ooking-after/invasive-species/japanese-knotweed

Notes to Editors

1.Images: Japanese Knotweed. Copyright SNPA