A SOCIAL housing construction project at Brews Hill in Navan was held up for almost a year to treat Japanese knotweed that was growing on the site.

The invasive plant is becoming a huge problem across the country and Meath County Council is ahead of the game in dealing with the stubborn and pervasive weed,

Meath has the third highest spend in fighting invasive species in the last four years, spending €814,000. The top two spending councils were Mayo and Cork, with total spends of approximately €1.28million, €950,000 respectively.

“Knotweed is becoming a huge problem across the state. I have seen signage warning of the presence of the plant in Mayo, Clare and Kerry over the years and assumed it wasn’t an urban problem. However, I’ve started to come across it more and more in Navan,” according to the Mayor of Navan, Cllr Eddie Fennessy.

“A local paving contractor cleaned the Thubberorum well during Covid and discovered the plant in the area. I’ve been made aware of cases in the Flowerhill area and a council direct build construction project at Brews Hill in the town was held up for almost a year to treat Japanese knotweed that was growing on the site.

“It is an invasive plant and quite difficult to treat. I advise people never to cut it under any circumstances, because that’s how it spreads. It needs to be treated with chemicals and that should only ever be done by qualified individuals.”

Japanese Knotweed is an invasive species that can out-compete native and more naturally occurring plants, so it has a direct impact on local biodiversity. It can have in-direct knock-on effects also. For example, when native flora is replaced by non-native plants such as Japanese Knotweed, this can have an impact on local invertebrate populations which rely on native plants for shelter, safety, and food. It can also be very problematic along waterways and impact the habitats we find along our riverbanks.

According to the National Biodiversity Data Centre, there is evidence to suggest it can be found in, or in close proximity to, several towns and villages across Meath, including Navan, Kilskyre, Oldcastle and Julianstown, among others. It is likely found in many other locations but has simply not been reported in recent years.

According to Meath County Council the approach to treating Japanese Knotweed depends on the location and circumstances it is found within. For example, along public roads the Council will treat it with the appropriate targeted chemical controls by trained users, whereas it may be more appropriate to tender for specialist contractors in other situations.

The difficulty with treating Japanese Knotweed is that after eradicating the above-ground growth of the plant, the below ground rhizomes might still be living. Therefore, continued monitoring of sites where Japanese Knotweed has been previously treated is advised.

Japanese Knotweed is a green shrub with bamboo-like hollow stems that grow to three meters in height and forms dense stands during the summer. In spring, small red buds appear that develop into ‘asparagus tip’ shaped stems. As it grows, it has a green stem with red/purple flecks. Leaves are arranged in a zig-zag pattern on the stem. Clusters of small creamy white flowers emerge in late summer.

In winter, the plant dies back leaving dead brown cane-like stems still standing or lying on the ground. Often, there is still evidence of browned flowers on stems. Underground, it has an extensive rhizome (which is essentially an underground stem) system commonly with an orange centre that snaps easily like a carrot when bent.

The council points out that landowners are responsible for ensuring that they do not cause or allow Japanese Knotweed to be dispersed or spread and should take action to control it, if it occurs on their property. It is an offence for anyone to cause or allow Japanese Knotweed to be dispersed or spread.

For information on what you can and can’t do to control Japanese Knotweed, the council advises landowner to research the various resources available from the National Biodiversity Data Centre and their Invasives website, invasives.ie.

In addition to Japanese Knotweed, Meath County Council is aware of other invasive species in Meath including Himalayan Balsam, Buddleia, Three-Cornered Garlic, Winter Heliotrope, Cherry Laurel, Giant Hogweed, Himalayan Honeysuckle, Rhododendron Ponticum, Spanish Bluebell and Traveller’s Joy.

The council points out that the control and management of invasive species is a national issue and requires a significant amount of resourcing.