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Kerry-based project is tackling the scourge of Japanese knotweed


Invasion species: Japanese knotweed

Invasion species: Japanese knotweed

Invasion species: Japanese knotweed

One of the most intriguing stands I came across at the Ploughing was the Japanese knotweed survey and awareness project.

Japanese knotweed is an alien invasive species that has no place in the ecosystem of Ireland. Since it was introduced as an ornamental plant in the 19th century, it has spread relentlessly across the island causing economic and environmental problems.

Native broadleaf woodlands are under threat as young saplings cannot compete for light. In the long term, the forests will fail to regenerate and with their loss comes the loss of many species that rely on them.

As it spreads along hedgerows and rivers, it breaks up the last remaining corridors for native plants and animals, dangerously reducing their habitats and gene pools.

It has become a very costly plant for the building industry. The cost of eradication before construction can be very high. It cost Kenmare hospital in excess of €100,000 to eradicate it.

The cost to the London Olympics to remove Japanese knotweed from the four hectare Olympic site cost more than £7m (€9.4m).

Any small piece of root or any knot on the stem will regrow. The roots can spread up to nine metres from the visible plant and three metres below. The most effective way to control it is to prevent spread. This means do not dig, do not cut, do not disturb.

Tackling it at the right time gives you the best chance of wiping it out. Optimum control will be achieved by treatment with glyphosate after flowering but before dieback.

The driving force behind this remarkable project is Jane Jackson who holds a degree in Environmental Science from the Open University. She launched the Japanese knotweed survey and awareness project in 2013 on the Dingle peninsula.

The project is working to curtail the spread of this species by mapping its extent throughout Ireland. The project is also raising awareness on how to prevent the spread of Japanese knotweed.

The project is carried out by volunteers with the support of Kerry County Council, the Heritage Council and Transport Infrastructure Ireland.

The project volunteers carry out a detailed survey between late spring and autumn. They record and date the sightings with GPS and photographs.

They also record any pertinent information. This is then put onto a map and made available on a website. All map data is shared with the National Biodiversity Data Centre.

Contact Jane Jackson on 086-1045979, email: kerryjapaneseknotweed

Steven Meyen, Forestry Adviser Teagasc

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