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Waterford City & County Council

Waterford City and County Council requests public to report knotweed

23 August 2016 Latest News Local News News

As the hedge cutting season is set to re-commence on 1st September, Waterford City & County Council is urging landowners and hedge-cutting contractors to be vigilant for Japanese knotweed growing in hedgerows.  Japanese knotweed is an increasingly common sight on the side of public roads, on waste ground and on the fringes of waterways.  It is one of the most problematic invasive alien plant species.  Japanese knotweed can seriously damage buildings and infrastructure by growing through concrete, tarmac and other hard surfaces if any cracks exist.  Japanese knotweed grows vigorously and out competes native plants.  It forms tall thickets up to 3 metres in height that exclude all other vegetation, shading the area below.  The principal means of spread of Japanese knotweed is entirely through the deliberate or accidental movement of rhizome fragments or cut stems.  Japanese knotweed has the extraordinary ability to spread and even tiny amounts of cut stem, crown or rhizome are capable of producing a new plant.  Controlling spread is therefore dependent on preventing the spread of the stem, crown or rhizome.  Landowners are being asked to be on the lookout for Japanese knotweed and cutting back or trimming of Japanese knotweed must be avoided.

Japanese knotweed can be identified by its hollow bamboo like stems which are green with red/purple speckles during summer.  The leaves are green, shield shaped with pointed tips and a flat base, 10-15cm in length arranged in zig-zag pattern on red shoots off the main stem.  It produces small creamy/white flowers in late summer and autumn.  During the winter the leaves die back and reveal orange/brown woody erect stems.

Japanese knotweed is best treated in situ using herbicide unless the site is being developed in which case material containing Japanese knotweed must be disposed of at a suitably licensed waste management facility.  The current most widely recommended chemical for the control of Japanese knotweed is glyphosate.  Herbicide containing glyphosate should be applied in late September or early October.  Equally, the plant can be treated early in the growing season (May) to stunt the growth of the plant.  Follow-up treatment will be required for 3 to 5 years and the location monitored beyond that to ensure complete eradication.

Waterford City & County Council is encouraging the public to report locations where Japanese knotweed is growing on roadsides, parks and open spaces.  The locations identified will be included in a Japanese knotweed eradication programme.  Japanese knotweed growing on private property can also be reported but control of the plant on private property is the responsibility of the property owner.

It is an offence to plant, disperse, allow dispersal or cause the spread of Japanese knotweed.  Members of the public can report Japanese knotweed by emailing  japaneseknotweed@waterfordcouncil.ie giving accurate details of the location, GPS co-ordinates would be ideal if you have a smart phone with GPS enabled.  If you don’t have access to email you can contact the Council’s Customer Service Desk on 0761 10 20 20 and report the location of the Japanese knotweed.

Further information on Japanese knotweed is available on the following websites.


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