The Kerryman (South Kerry Edition)
Call for calm in debate over battle against invasive knotweed
NATURALIST JOHN LAVERY CALLS FOR CALM IN THE DEBATE SURROUNDING INVASIVE JAPANESE KNOTWEED
JAPANESE knotweed, scientifically known as Fallopia japonica, is a member of the knotweed and buckwheat family. It is a tall, perennial plant, typically reaching a height of two metres. Its creamy white flowers appear in abundance during late summer through early autumn and give the plant an attractive and exotic appearance and it would be reasonable to expect that this is what drew collectors and, later on, Victorian gardeners to acquire it in the first place.
In Ireland these flowers are much frequented by various butterflies, bumble bees, honey bees, wasps, longhorn beetles, hoverflies and a host of other insects which find an important source of nectar, particularly when so little else is in flower late in the season.
Though it can be claimed that stands of knotweed shade out native plants it can be observed that delicate and beautiful ferns such as Hart’s tongue will thrive beneath them. Generally the rural sites I have visited to record the native flora have shown that the plants being crowded out were bramble, nettle, soft rush, creeping buttercup and common grasses all of which tend to be invasive species themselves and could never be considered to be in need of protection.
Japanese knotweed’s presence in the vicinity of rare plant species would of course be a matter of concern, but this would be unique or at least to date has not been of concern.
In Japan, it has always been foraged as a wild vegetable food source where the young leaves and shoots which resemble asparagus are widely eaten.
All the plants growing worldwide are known to derive from one root stock collected in 1820 by a Dutch collector called Philip Franz Von Siebold and at first planted in Holland when he returned to Europe sometime in 1822. It multiplied quickly and one of the resulting plants was presented in 1850 to the Royal Gardens in Kew. It soon found its way into private gardens and even took top prizes in prestigious flower shows in those early days of its history.
Knotweed became a hit, a ‘must-have’ for Victorian gardeners in the late 1800s, easy to grow, lovely flowers, taking to any type of soil, and resembling exotic stands of bamboo which were all the rage at the time. And and so it is that from that one plant all others beyond the Orient have their origin.
A combination of it becoming too common and crowding out the smaller and more delicate sun-loving plants with which it shared these great pleasure gardens saw it begin to fall out of favour and so, like many unwanted things, it was thrown out of the walled gardens onto waste ground where it soon began life as a true wild thing for the first time outside of its native climes. This process began in the late 1800/early 1900s.
Soon it was being tried out successfully as an animal food, however. The practice is well recorded in Central Europe, and also closer to home, in Wales. Of course it is reasonable to surmise that its use as an animal fodder led to it soon becoming a human food source and it is documented that this quickly happened.
To the present day it is foraged in many parts of the world and experiments are being carried out at Cardiff University where it is used as a cattle fodder on the model farm there. It grows in 29 of the American states and parts of Canada where it has also been used as human food vegetable, the young leaves and shoots cooked like spinach.
Now one would expect from the rash of horror stories emanating from the internet through social media and such like that the plant had suddenly and only in recent times arrived to our shores, but the undeniable truth is that it has been here for well over a hundred years and up until recent times has given us not the slightest concern. Its spread in Ireland began in the 1980s and has not abated since.
So what has happened? Why has a plant sitting quietly in many a kitchen vegetable garden for the past century become the monster and public enemy number one of the plant world?
When I was a boy in the 1950s almost everyone worked a vegetable garden and only plants that were used for human or animal food were given space. In other words any plant that could not feed animal or human would not be allowed to flourish. At the southeast end of our garden a small stand of
Japanese knotweed grew and though it was never used as a food source by us it was fed throughout the growing season chopped up for pigs and so our little patch at best managed to replace its stalks and never had any reserves to enable it to enlarge its position or dominate in any way.
I mention this only to illustrate that it can be a lot easier to control than popular opinion would have us believe. Back in the 1950s it was rare to find Japanese knotweed away from dwellings, but as practice of feeding it to livestock went out of fashion that would change and the pleasure garden plant formerly rescued from the tip and used for a time as an animal food source would again become a plant that nobody wanted and was consigned to the hedges the roadsides, and railway sidings.
From these small groups of discarded plants the advance began and with knotweed’s lack of preference for a particular soil and the fact that it can spread from the smallest root fragment it soon expanded its range in the wild.
It does not produce viable seed from the flowers as all the plants are female, so all spreading and development of new sites has to be by human disturbance, which can come through innocent transportation of as little as a small piece of root stock or, of course, by dumping simply to be rid of it, when the site on which it is growing is being developed.
It can even arrive to you in a lorry load of top soil, which happens often.
A very recent incident comes to mind, last February 2017, I observed work being carried out. Soil mixed with stone, and other organic material was unloaded from a dumper off onto the edge of the raised road side where a digger was tapping each load into place.
This work took two days to complete and extended over 200 metres. In the weeks that followed the bank greened up as grasses took over, followed by the unmistakable shoots of Japanese knotweed which of course were abundantly mixed in with the soil. It took only two days of carelessness to produce this new site which has grown to maturity in the months past.
How many times has this happened before, and how many more times will it be repeated?
The progress we make as we expand and develop sites in our ever growing villages, towns and cities is directly linked to the growing occurrence of knotweed. It is all to easy to clear one site and dump the offending material in perhaps several sites. We have to face the reality that this has and still is happening. Of course the only thing we know for certain about this plant is that it is spreading through human action, but whether there is any real grounds for considering that Japanese knotweed is a rising menace it remains factually unproven.
On the one hand it seems there is insufficient data to establish many of the accusations made. While on the other hand in view of the persistence with which the horror stories crop up in different countries, it would be presumptuous to dismiss it as groundless.
My personal view is that the so-called threat from Japanese knotweed is very much exaggerated and comes from within the industry set up to eradicate it. In the 150 years since its introduction its ‘invasion’ has failed to destroy even one building or rip up a road so where is the menace?
Furthermore as regards growing through solid concrete this has to be an urban myth. It is well known that any plant taking root in a crack will, as it grows, exert enough pressure to expand the opening and cause further damage.
Our natives, ivy, alder, elder and willow are prime examples of plants that exploit cracked pavements and other compromised surfaces and if left unchecked cause massive damage. Do we also set about eradicating these species?
With Japanese knotweed all the evidence makes for very minor damage to the manmade environment. Any plant will invade a crack in concrete but a well-built modern building compromised by knotweed is just pure fantasy. Yes, an old dilapidated building or badly laid drive way full of gaping cracks can be further damaged if roots of knotweed push through but many other plant species could equally find a niche in similar conditions.
The plant, as with all invasive species be they alien or native, is without a doubt a headache more especially when found growing over a large area. The only option for removal is through the use of herbicide and to kill it off entirely will take time, up to three years in some cases.
Digging out the living plant and incinerating it would provide a sure way to wipe out the plant but we don’t have that facility in the country.
To date hard-pressed taxpayers are not being well served by the hysteria which is being generated from inside an industry which has mushroomed almost as soon as the monies to combat the Japanese knotweed ‘problem’ became available. No consensus has been reached on anything in relation to this plant which might lead to a solution, but there is no let up on photo opportunities from across the political divide.
Internet sites are so similar they might as well have been written by the same person; exaggerated horror stories with very little substance and pictures of minor invasion through very compromised environments abound.
This armchair conservation approach in itself is only leaning towards an alarmist point of view and bears no relation to reality and has become tiresome in the extreme. Internet sites are notorious for peddling many of the myths which so often go unchallenged and end up as accepted facts in the mainstream media.
There is also a very real danger that the industry will with such unfounded stories talk up legislation and this has happened in other countries where having even one plant on your property could lead to an on the spot fine. And it won’t stop there, the offending plants will have to be removed by ‘experts’ with charges at the lower end of the scale being in the region of €2,000.
It might be the better option to leave existing sites untouched for the present and instead embark using public service employees on a mapping survey and GPS all known locations. In this way the extent of the problem can be recorded and at no great expense as the peoplecarrying out the work are already on the payroll. Not another cent should be spent on outside contracts in relation to this so-called invasive species until a complete picture of its present status is on record.