Regional council to target invasive Japanese knotweed
All that glitters is not gold . . . The dense foliage of the Japanese knotweed.
A HARDtodestroy ‘‘concretecracking superweed’’ capable of damaging building foundations and pushing up roads has been found in several Dunedin locations.
The Otago Regional Council confirmed Japanese knotweed had been found on Mt Cargill, the banks of the Water of Leith towards north Dunedin and in Wakari and Helensburgh.
The council is to send out contractors to undertake control of the weed at these sites for the first time this spring.
Environmental implementation manager Libby Caldwell said the weed could have an adverse effect on biodiversity and native plants, and cause damage to amenities.
‘‘[They form] dense thickets which can exclude other species and prevent native seedlings from establishing.
‘‘They can also damage building foundations, push up roads, narrow waterway channels, impede water flow, leading to siltation, and impact on recreational values of waterways, such as fishing and birdwatching.’’
If knotweed was left uncontrolled, it had the potential to spread. It had already caused serious issues in Waikato, NelsonTasman, the Bay of Plenty as well as Australia and the United Kingdom where media have labelled it a ‘‘concretecracking superweed’’ .
The weed was difficult to eradicate because it was invasive and had extensive root systems which could extend 7m horizontally and up to 3m deep.
‘‘They could tolerate high temperatures, high salinity, drought and a range of soil conditions and can be difficult to control with regular control methods.’’
Japanese knotweed was identified in the Otago regional pest management plan 201929 as an organism of interest.
Anyone who spots it should contact the council’s biosecurity team at biosecurity@orc.govt.nz or 0800 474082.
A 2019 British parliamentary paper said the weed cost the United Kingdom £166 million ($NZ328 million) per year, which included the cost of treating the plant in the rail and road networks and property devaluation.
The Guardian reported that it cost one homeowner more than £10,000 to hire workmen to remove the weed from his property.