Invasive species threaten our native biodiversity, can cause havoc on the recreational value of an area and have negative economic consequences for local industries. They cost Europe around €10 billion annually with the UK spending £2 billion on their management last year. The total monetary impact for Ireland is not yet known.
National Biodiversity Data Centre - Invasive Species Survey - 2009
In Ireland, there is a need to know what invasive species we have and where exactly they are. This information needs to be up to date to effectively inform decision making and management of the species. It is often very difficult and costly to eradicate or control invasive species once they have become established so the 'earlier the better' is the motto for recording invasive species.
What can be done?
The National Biodiversity Data Centre is rollilng out an all Ireland survey on eight of Ireland's most unwanted invasive plant species. To take part in the survey all you have to do is record information on the whereabouts of these invasive species and submit that data to the Data Centre. This can be done by filling out the online submission form http://invasivespecies.biodiversityireland.ie
Additional survey information and species identification support is also available from this website or by contacting Colette O'Flynn - coflynn@biodiversityireland.ie or phone (051) 306 240.
Japanese Knotweed in Offaly
Japanese knotweed has been found in Offaly - but hopefully with awareness and treatment it can be contained and minimised. In 2009, records of all known locations have been gathered by the Heritage Office and all relevant sections of the County Council have been made aware of the issues involved, particular the spread of Japanese knotweed by hedge and verge cutting and movement of soil. A number of the sites have been treated and will need ongoing treatment and monitoring.
Background
This menacing plant, introduced to Irish gardens in the 19th century as an exotic, has become one of Ireland’s 10 Most Unwanted Invasive Aliens. Able to grow a meter in less than a month, Japanese Knotweed can push through concrete and tarmac. Meanwhile, its roots can spread 7 metres wide and 5 metres deep. In no time at all, Japanese knotweed can create an impenetrable thicket 3 m high.
Its unusually deep leaf litter smothers rival plants and wipes out native species. But even when it isn’t visible above ground, Japanese knotweed can lie dormant, but very much alive, below ground for up to a decade.
Years after projects have taken place to remove Japanese Knotweed, it is not defeated. Because it lies dormant underground hibernating, every year the area must be scoured for re-growth. Unless the plant is constantly monitored, the area will be covered in knotweed again in a number of years.
What does it look like?
At this time of year Japanese Knotweed can reach three meters in height. It has green sheild shaped leaves and spikes of small, creamy white flowers. In the autumn it sheds its leaves and becomes an unattractive, stand of dead, brown hollow stalks that rot over the winter. In the spring, little dark red shoots like dragons’ tails emerge. Growing up to 4 centimeters a day, they quickly form bamboo-like stems which sprout green leaves. Its roots are dark brown with a bright-orange inside which can snap easily, like a carrot.
Why is it a problem?
It beats native plants
Few plants new to Ireland are as invasive or destructive as Japanese knotweed. It can take over an area, wiping out all other plants—including our precious native species—in a single season. It does this by blocking out light and the deep leaf litter presents new growth of native plants. These native plants are just one part of the whole biodiversity story and this is all affected when Japanese Knotweed can quickly become the only game in town.
It is destructive on building sites
The ability it has to grow through tarmac and concrete makes it a disaster on a site where work is to be carried out. Unless comprehensive eradication work is done, the Japanese Knotweed can disturb the site for years to come. It is essential to stop the spread of this plant to save having to spend to eradicate it before work is done.
It is a hazard on the road side
On the road side, as it grows so quickly, it can block site lines only weeks after it is cut – so while the native plants are only inches high – it is leaping back up in meters.
How does it spread?
Without knowing it, people help Japanese Knotweed spread. Every Japanese Knotweed plant in Ireland is female. The only way it spreads is through its rhizomes or fragments of its own vegetation breaking off and re-growing. This means that when people cut it to try and get rid of it they actually help it to form new clumps. Strimming it is the worst thing you can do as it creates millions of tiny pieces, each of which can sprout into a new plant. Any cut or broken material should be burnt.
A real accelerator in recent years has been the moving of contaminated topsoil and building material around the during construction and road projects.
Lack of knowledge about how it spreads has meant that hedgecutting contractors have been cutting and spreading it unknowingly. Very often when there is a roadside area of knotweed, there are several clumps further down the road where sections from the flail cutter have landed in previous years.
What can you do to stop this menace?
DON'T IGNORE IT. . A small Japanese knotweed plant quickly becomes a major infestation.
Do not strim, flail or chip it. Japanese knotweed can reproduce from tiny needle sized fragments of rhizome, twig or even leaf. It is extremely unlikely you can eradicate it by digging it out, because the roots stretch down so deep into the soil.
Notify Offaly County Council of any locations – If you think you have Japanese knotweed, or you’re not sure and need help with identification, call the heritage officer at 057 9346839 or email heritage@offalycoco.ie.
September is the time to begin to take action - Spray and monitor identified clumps. Where you have a confirmed site, spraying with Roundup in the second half of September means that as the plant dies back for the autumn, it will pull the herbicide down to its roots. This is the most effective time to spray. However the site will need spraying next year in the spring when it is about 1 metre high, again in mid summer and again in September if the leaves are still green. It will need continued attention and spot spraying to stop it re–emerging. Do NOT spray if you are near a watercourse.
Check sites are free from Japanese Knotweed before soil is moved. Because it is such a problem to control it is particularly important not to let new sites establish and contaminated soil should not be moved.
Act now!
In London, the Olympic site is facing a bill of £70 million plus to remove the Japanese Knotweed from the site – the eradication bill overall in the UK is in billions – we have a chance, in Offaly, to act and to keep costs down for infrastructure projects early and avoid loss of native flora and fauna in the future.