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Home: Community full menu: Environment
Japanese Knotweed
David Hosley - March 2005
david.hosley@kirklees.gov.uk
Japanese Knotweed Policy
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How to identify Japanese Knotweed
Upright clump forming habit of up to 2-3 metres high. The truncate stems and leaf stalks are red in colour. Leaves are broad and ovate
with a lighter green underside. Flowers are white and plentiful with axillary panicles. Flowering period is from August - October.
Japanese Knotweed was introduced into Britain around 1825, and since then has become so widespread that it has become a serious weed
problem. It is a perennial plant with an extensive system of underground rhizomes that is very invasive that may reach a depth of 2
metres and extend to 7 metres from the parent plant. Fortunately the plant does not set true seed owing to the absence of male fertile
plants, but regeneration of the plant is vegetative and can occur from the smallest rhizome fragments and is the primary method of spread
within a site and between sites.
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Why should I be concerned about Japanese Knotweed ?
The presence of the weed on land is not an offence, but under the Wildlife and Countryside Act it is an offence to spread Japanese
Knotweed, and any material containing Japanese Knotweed taken off a site must be safely contained and disposed of at a licensed disposal
site according to current guidelines (Environmental Protection Act - Duty of Care - Regulations 1991)
How to control Japanese Knotweed
The control and eradication of the weed is the responsibility of the Land Owner, and on sites where it is present a policy of control
leading to eradication should be followed.
Herbicides that target the underground rhizome system offer the most effective method of control. A chemical application applied to the
whole leaf growth at a height of 1 metre has been found to be the most satisfactory control during active growth. If the growth has
become woody, the stems should be cut and the new growths sprayed.
Control methods advised are:
Chemical control with glysophate in spring on young growths, or treating both sides of leaves in august are partially successful but
further applications may be required.
Chemical control with Tordon 22 on land not intended for cropping or garden use has found to offer excellent results as it is a
persistent selective weedkiller that can be effective up to two years Chemical Trade names recommended for control include Roundup,
Garlon 4, Tordon 22 and Evade, all applied at the recommended application rates available from Garden Centres or Horticultultural Trade
Suppliers.
Grass cutting and Japanese Knotweed
Knotweed can be found growing on or adjacent to areas of Council owned land. As recent research has shown that the plant can be spread
by the smallest amount of cut stem material extreme care should be taken to ensure that areas of Knotweed are not cut , flailed or
strimmed unless the work is being undertaken as part of an agreed control operation. Where regular grass cutting or Highway flail mowing
is undertaken and an area of knotweed is identified no mechanical contact should be made with the plant, as it is possible to cause the
spread of the weed by the transfer of the smallest part of cut material becoming attached to the cutting equipment potentially being
transferred to the next site visited by the Contractor. Any material cut accidentally shall be either dried and burnt completely or
bagged and removed to a controlled tip. The Contractor should cut around the infestation to ensure that no contact is made with the
Knotweed and report the location to the Client Service responsible. The potential risk and dangers of the infestation can then be
assessed and appropriate action to control the Knotweed undertaken.
Further advice
Technical advice on Knotweed and help on the control and eradication of Knotweed can be sought from Defra website www.defra.gov.uk. The
reporting of Knotweed locations and advice on its control can be made to Kirklees Council using the ROSS freefone service
on 0800 731 8765 or Culture and Leisure Services on culture.and.leisure.services@kirklees.gov.uk.
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