It creates such dense and high growth (2-3 metres)
that native plant species are unable to compete with the tall summer growth or
the thick mulch of decaying canes in winter. Many insects that depend on native
plant species are lost.
Japanese
knotweed was introduced in the 19th century as an ornamental garden
plant. Now it is the most widespread and troublesome bank side species.
It creates such dense and high growth (2-3 metres)
that native plant species are unable to compete with the tall summer growth or
the thick mulch of decaying canes in winter. Many insects that depend on native
plant species are lost.
A piece of root
(rhizome) the size of a little fingernail is enough to create a new plant. It
can also be spread by crown (base of stem) or stem node segments. The root
systems can extend under motorways to pop up the other side. The plants have
been known to force their ways through tarmac, walls and foundations.
Under the
Wildlife and Countryside Act 1981, it is an offence to spread Japanese Knotweed.
Civic Amenity green waste composting schemes are not suitable for receiving
knotweed, unless the material consists of dried cut canes with no associated
crowns.
The view of
Pembrokeshire County Council (PCC) is that if we do nothing we will lose our
biodiversity. So far in Rosebush and Ambleston Common PCC has achieved 95%
eradication in the last 3 years.
If as a
community, St Dogmaels would like this plant controlled Pembrokeshire County
Council (PCC) can assist, either by spraying or giving advice on the other
methods available.
Many people are unhappy about spraying but there is
no simple solution.
At present the
only sure way to eradicate knotweed is by chemical treatment,
mainly spraying
with glyphosate. The Environment Agency and Countryside Council for Wales back
its use as the most practical method yet available. It is used in Areas of
Special Scientific Interest (SSSI), Special Areas of Conservation (SAC) and the
National Park. You can spot treat or use 2,4-D amine, which is specific to
broad-leaved plants and will not harm grasses. Autumn spraying is most
effective. Eradication may take 3 years.
Sites near
watercourses can only be treated if the Environment Agency grants an approval
licence.
Stem injection
can be used in which the plant is cut at 10-15 cms above the crown and herbicide
injected into the hollow stem. This
targets only the knotweed.
Spraying with
hot water and coconut sugar (the Waipuna system) has been used. It works well
for annual weeds, but is not good on knotweed. Waipuna has a good website.
The cut stem
cannot re-grow once it has dried to a dark brown colour, however the crown can
survive drying and composting. Use a simple scythe. Avoid fragmentation e.g.
with strimmer or flail. Cut every 2-4 weeks to reduce biomass above and below
ground. Burn cut stems on site. This method of repeated cutting to weaken the
plant may take up to 10 years to eradicate it.
For the
enthusiastic – Dig around clump for up to 7metres (& up to 3 metres deep)
and sieve through 20mm mesh. Burn root and stem fragments
Uproot stems by
pulling from base, best done from June onwards. Pulled stems will include
crowns. They should be dried on a layer of polythene to prevent rerooting. Burn
root and stem fragments on site or bury at least 10metres deep.
Grazing of
shoots by sheep, goats and horses keeps the plant in check provided previous
dead growth is removed
Disposal off
site can only be done to a landfill operator licensed to deal with knotweed.
A bio control
project is also being trailed but will not be at the release stage for
approximately 7 years.
In the meantime
PCC are continuing to carry out chemical treatment on Council land to protect
the biodiversity of the countryside. The Environment Agency and Local Government
are not obliged to control it on behalf of other landowners. Responsibility for
the control of knotweed rests with the landowner or tenant. If knotweed is
coming onto your land from an adjoining property co-operation is the best
approach.
The Community
Council is in the process of mapping where the Knotweed is.
If you know of
knotweed that needs mapping, contact Gill Wislocka or Mike James.
Sept. 2004
For further
knotweed information contact:
