VIDEO: Knotweed is a growing scourge on the environment

This is the insidious Japanese knotweed, one of the fastest-growing and most destructive of our adverse invasive plants and weeds.

VIDEO: Knotweed is a growing scourge on the environment

It is becoming an increasingly common sight along roadways, walls, and private property, including gardens, countrywide. Forty years ago, it was relatively thinly spread but it is now out of control in many instances.

For the past three years, Kerry county councillor Michael Gleeson has been campaigning for an eradication programme in his native Killarney, which also has a national park to protect, and is now calling for co-ordinated action at national level.

“No-one listened for quite some time and the plant continued to prosper. However, action has been taken in the past year, or so. There are signs that the knotweed is disappearing but it can also grow in new places very quickly,” he said.

He’s confident the eradication project, which involves spraying herbicides on the plant and injecting stems when the plant is found near watercourses, will, eventually, destroy knotweed.

“Public awareness is hugely important but, equally, it has to be ensured that all staff involved in eradication work are properly trained. If the plant is simply cut, for instance, that will only lead to its further spread.”

It spreads by regeneration, even tiny pieces of the plant grow into new plants. A person working in their garden and trimming plants can inadvertently facilitate knotweed spread by strimming, digging it up, or composting.

Killarney Town Council, abolished a year ago, took decisive action in its final year by means of injection and, hopefully, has eliminated the knotweed, especially in sensitive areas on the edges of the national park. Identification signs have been placed along the N22 Cork/Tralee road, outside Killarney, warning people not to cut or pull the plant.

However, Mr Gleeson also heard last year of the plant being cut along the sides of some roads. He assumed this was because some people were unable to identify it. He has called on the municipal area engineers and foremen to ensure that they can identify the knotweed and to convey the necessary information to all outdoor staff. Also, he visited two locations where knotweed was sprayed last year and had very clear evidence that one spraying was insufficient.

David Doyle, senior operations engineer, Kerry County Council, said council staff sprayed the plant with chemicals in Killarney and general east Kerry area that worked in the past few years.

“This has been successful in the vast majority of areas treated as the plant has not reappeared. But the spraying has to be done over a three-year period in September/October. Otherwise it may grow again. We will be spraying each year,” he added.

Signs have also been put on infested roadsides in rural areas advising people not the cut the plant and to contact the council first.

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