the Lyreacrompane area
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What is Japanese Knotweed?
A worldwide invasion!!!
which can grow through
show Japanese Knotweed in full bloom and as a young plant forcing its way up
through tarmac. It is a rhizomatous perennial that can grow
rapidly to a height of up to 10 feet. The roots of a single
plant can extend for 20 feet and can be found 6 feet below the
Red/purple shoots appear in early spring. As the
canes grow, the leaves unfurl and the plant turns green.
Mature canes are hollow and have a characteristic pattern of purple
speckles. The leaves are carried on stems in a distinctive zig-zag
pattern. Flowering occurs in late summer/autumn and consists of
clusters of creamy white flowers. During the late autumn and
winter, the canes lose their leaves and turn dark brown. The dead
canes remain standing. The plant lays dormant underground for the
winter and reappears again in the spring.
close look at the leaves and
Japanese Knotweed in full flower
did it come from? Japanese Knotweed was
introduced as an ornamental and fodder plant in the 1840s. It came
into a new environment in Ireland without its natural enemies that
keep it in check at home in Eastern Asia.
Other names for Japanese Knotweed are Sally
rhubarb, donkey rhubarb, gypsy rhubarb, Hancock's curse, Pysen saethwr,
Glúineach bhiorach, Mexican bamboo, Japanese bamboo, Japanese
fleece-flower, wild rhubarb and crimson beauty.
it be a cause of concern?
very invasive, totally out of character with the Irish landscape,
overpowering native species and is of little value to wildlife. As
in parts of Britain, Knotweed infests the banks of rivers as it is
quickly dispersed by water. The river Smearlagh in the Stacks/Glenaruddery
Mountains of North Kerry is endangered in this regard – a matter of
concern to anglers.
Japanese Knotweed found its way into the wild?
Luckily, Knotweed does not have viable seed
(although there is a danger that cross pollination with distant
members of the same botanical family such as Russian Vine may bring
that catastrophe about). The plant is spread by human
activity. Unfortunately, extremely small bits of the root will
reproduce. They are carried from site to site on the wheels
and tracks of earth-moving machinery and on the wheels of trucks,
JCBs and tractors. This is why you will often find dense thickets of
Knotweed at gaps and entrances into fields and sites.
The River Smearlagh in Lyreacrompane, Co Kerry in
danger of serious infestation and
Knotweed in December beside a
roadway and stream in Lyreacrompane.
Knotweed is also spread by illegal dumping in our
bog lands, boreens and isolated spots. This dumping arises out
of generally vain attempts by people to remove the weed from their
property – rarely successful, as the smallest piece of root or crown
left behind will regenerate! So now, instead of
one infested site, we have two - and more in the making if the roots
are dumped anyway near a river or stream. The action of
flowing water carries parts of roots down stream where at various
locations they find landfall.
What can we
do about the Knotweed invasion?
The first task is to stop the matter getting
worse and then begin to take steps to clean up yet another fine mess
we have made of the environment. Information and education
on the problem is the first step. So spread the word!!!
Digging up the plant rarely succeeds, as it is almost impossible to guarantee the removal of all root parts.
Sections of rhizome (root) as small as 0.7 of a gram can grow
into a new plant. (If digging is undertaken the material must
be disposed of in a managed landfill site).
Japanese Knotweed in Limerick, Ireland looking
fresh in Mid-November. This was new growth following ground
Cutting the plant to the
ground, a couple of times in late summer, with a loppers or a scythe
(do not use a mower or a strimmer) will deprive it of the ability to
convey nourishment to the roots. Employing this method over a
number of years will greatly retard the plant and will (probably)
eventually kill it. All stems cut down should be burnt on site or
taken to a managed Landfill. (Do not include cut stems in home or
Council composting projects.)
machines. Drivers of earth moving
machinery should get to know Japanese Knotweed and avoid contact
with the plant when working on site. Wheels and tracks should be cleaned down before leaving
an infested site.
Japanese Knotweed is palatable to sheep, goats, cattle and horses
and grazing may be used in suitable situations to keep the plant
under control. Some experts say there is evidence that persistent
grazing (or cutting) in the spring can actually strengthen the roots
and lead to a stronger re-growth if the practice is stopped.
The most effective strategy against Knotweed is the application of a
herbicide containing a formulation of
Glyphosate in September.
Spring treatment is
acceptable, but less effective. This treatment should kill off
Japanese Knotweed in three years. (Always carefully follow the
instructions in relation to personal safety, other plants and use
near water when using Herbicide.)
Japanese Knotweed hit be rust - a natural enemy in its native east
Control. Japanese Knotweed was
introduced to Ireland without any of its natural enemies. Trials
are underway in Britain to identify safe and appropriate predators
and pathogens that can be released into the environment for the
purpose of debilitating the plant and thus make any subsequent
control easier. The outcome of these trials may take a number of
years but hopefully they will produce results that will allow the
Knotweed, which is inappropriately growing in the wild, to be
Knotweed in Kerry, Ireland.
In the first instance, this webpage arose out of concern for the
spread of Japanese Knotweed in the Lyreacrompane district of north
Kerry, Ireland. It is a moor land area in the Stacks
Illegal dumping and earth moving machinery have introduced
Knotweed to this classical peatlands setting. The rapid and
quick flooding streams and rivers have taken the initial infestation
and spread it further and further.
Through this webpage and other media we hope to establish the
true extent of the infestation in all of County Kerry and to
encourage individuals, organisations communities, local authorities
and state bodies to work on the problem.
Tell the Carriers!
Many drivers of earthmoving
machines are totally unaware that they may be distributing Japanese
Knotweed as they move from site to site. If you know any you
should draw their attention to this webpage.
Specifically, in relation to Kerry visitors to this site we would
ask you to check out the problem on your area and e-mail us
your findings. Most of the Japanese Knotweed will be found
along the road side and on the banks of streams and rivers.
This makes it relatively easy to track down.
Your survey should include
-the name of the stream or river and the part of it surveyed.
-the location of the stretch of road surveyed.
-the approximate number of clumps in the stretch of river or road surveyed.
-information on the approximate size of the clumps, i.e. 5 feet
by 5 feet, 10 feet by 7 feet etc.
-information on urban infestation would also be welcome.
E-Mail any information you collect to
We would be
delighted to carry your messages, opinions and accounts of your
experiences with Knotweed in this column. You can e-mail them to us at