Ireland's efforts evolve over half a century to try and control the invasive rhododendron

Rhododendron was introduced into Britain and Ireland from Asia and the Iberian Peninsula in the 1760s. It was planted on demesne lands for ornament, shelter and as cover for deer and fowl in woodlands.

But it is now widespread on locations from Donegal to southwest Cork and from Connemara to east Dublin. There are more than 900 species of the colourful plant worldwide, but only one type, Rhododendron ponticum, is invasive in Irish habitats.

It blocks light, reduces biodiversity, suffocates other species and is the bane of environmentalists.

As many as 7,000 seeds can be produced per branch and these are readily carried by the wind. They can also be spread vegetatively, increasing their invasive potential.

Methods of eradication includes removal from the root base, chemical spraying of stumps and injection of shoots with herbicide. Various agencies in Britain and Ireland have spent time and resources in attempting to control the spread of the plant but have found it a slow and ongoing battle.

Cork South-West Fianna Fail TD Christopher O'Sullivan recently raised issues relating to the infestation in Killarney National Park. Minister of State Malcolm Noonan explained that the National Parks and Wildlife Service (NPWS) is committed to tackling the spread of species across the national parks network.

He said the control of Rhododendron ponticum is difficult, costly, and labour-intensive, but is seen as a vital priority.

The NPWS carries out an annual targeted programme of works across a number of sites to manage the spread of the plant. The multi-faceted programme includes monitoring, surveillance, clearance, investigation, review, volunteer and contractor work groups and programmes.

“Rhododendron has indeed been a major factor causing degradation of habitats in Killarney National Park.

“Efforts have been ongoing in the last 40-50 years with a variety of partners in order to tackle this issue and in this period a tremendous amount of work has been carried out by volunteers, contractors and staff.

“Despite these efforts there is still a lot of work to do. The effects of Rhododendron ponticum is well documented both in Killarney National Park and also in other sites across Ireland and the UK.

“The method of treatment has changed and evolved over the years and the current method developed in Killarney National Park is considered to be the most suitable solution at this time,” he said.

The park is divided into zones, which include woodland, wet and dry heath and blanket bog. Monitoring allows staff to develop a strategy for treatment, picking areas for prioritising work.

He said the NPWS commissioned a review which will set a strategy into the future. One recommendation was to develop management plans for each zone. Staff at Killarney National Park are currently developing draft plans.

The minister said treatment of Rhododendron ponticum is continuous, with work underway in the park’s western woods. These areas will be resurveyed next year. Following the results, it is expected that the NPWS will be able to classify a large area as being in a “maintenance” phase.

In the last five years, there has been approximately €2.7m spent on rhododendron management at Killarney National Park between treatment and monitoring. Close to 2,000 acres of area has been treated.

Minister Noonan said in the next five years there will be a continued effort to move zones. All of them will be monitored to ensure the maintenance status.

Just as the methodology employed to control Rhododendron ponticum has evolved over the years, so too have the groups, contractors and individuals involved in these efforts.

“This is something that the NPWS expects will continue to evolve across all our sites into the future,” he said.