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Japanese Knotweed is a hardy ‘bamboo like’ plant that was imported from Japan in the 1850’s. This weed causes many problems on development sites and residential gardens. It is a particular pest along waterways and railways where it colonises bare land very rapidly. |
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Japanese Knotweed is a tall perennial plant. This means that it dies back in winter and re-emerges in spring. The shoots start to emerge in late March / early April, are ‘asparagus like’ and are a red-green colour. As it grows through the summer the red colour turns into red speckles on an otherwise green stem. At full height it can reach up to 3m. The leaves are bright green and roughly hand sized in an almost heart shaped fashion. In September the plants develop small white flowers which in some cases can be so abundant that they almost completely cover some sections of the plant. Around November time the plant drops its leaves and flowers. The hollow brown and brittle stem remains as a clearly visible indicator of where the plant stood in the summer. The next year the plant will re-grow from the same spot out of what is known as the crown. |
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For more photos of Japanese Knotweed please see the Japanese Knotweed Pictures Gallery. |
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The Invasive Plant Company offers many different types of remediation strategies for the eradication and management of Japanese Knotweed: The following shows a selection of those available, all of which are covered by an insurance backed guarantee. |
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Herbicide spraying program |
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A Herbicide Spraying Programme can provide a cheap, effective and simple strategy to treat Japanese Knotweed and is an ideal method for treating Japanese knotweed in parks, gardens and alongside rivers and railways. However, to be effective the treatment needs applications over a number of years away from any groundwork activities. As a result this method is not usually suitable for development sites |
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Excavation followed by stockpiling and herbicide treatment |
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This method is often the next cheapest alternative compared to spraying. Excavating the Japanese Knotweed material and stockpiling elsewhere on site allows for development in the originally contaminated area to proceed immediately. An added benefit of this is that the excavation process can stimulate growth in the Knotweed that herbicide treatment alone would not, allowing the treatment to be completed quicker. As the material is excavated and treated on site it saves transportation costs, however does require adequate space to stockpile the material on site for a minimum of a 12 month period. Due to the nature of the pesticides used, the stockpile cannot be located near water. |
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Excavation followed by sifting and burial |
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The sifting process aims to remove all the Japanese Knotweed material through a combination of mechanised processes. This effective and quick method of dealing with the Japanese Knotweed on site means with most sites the remediation process can be carried out within a number of weeks. This is also the most environmentally friendly of our treatment methods as it uses no persistent herbicides, however, it can be labour intensive. |
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Removal to Landfill |
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This method completely removes Japanese Knotweed material from site and is very quick to implement.
However, with
the increasing costs of haulage
this can be expensive for large
areas of Japanese Knotweed and
raises sustainability
issues.
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Reduced excavation and insertion of geotextile membrane |
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A reduced excavation vastly reduces the amount of material to be dealt with and hence the cost and timescales involved, although it does require careful liaisons with key stakeholders to ensure all contractors working on site are aware of the Japanese Knotweed excavation/geotextile works |
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The following legislation refers directly to Japanese Knotweed and the handling and disposal of it: Section 14(2) of the Wildlife and Countryside Act 1981 (WCA 1981) states that “if any person plants or otherwise causes to grow in the wild any plant which is included in Part II of Schedule 9, he shall be guilty of an offence.” Japanese knotweed is one of the plants listed in the Schedule. Anyone convicted of an offence may face a fine of £5,000 and/or 6 months imprisonment, or 2 years and/or an unlimited fine on indictment. The Environmental Protection Act 1990 (EPA 1990) contains a number of legal provisions concerning “controlled waste”, which are set out in Part II. Any Japanese knotweed contaminated soil or plant material that you discard, intend to discard or are required to discard is likely to be classified as controlled waste. The most relevant provisions are in: section 33 (1a) and (1b) which create offences to do with the deposit, treating, keeping or disposing of controlled waste without a licence. Exemptions from licensing are available in some circumstances, and are set out in Schedule 3 to the Waste Management Licensing Regulations 1994 as amended (the WMLR 1994) s.33 (1c) which makes it an offence to keep, treat or dispose of controlled waste in a manner likely to case pollution of the environment or harm to human health. Section 34 places duties on any person who imports, produces, carries, keeps, treats or disposes of controlled waste. Waste must be handled responsibly and in accordance with the law at all stages between its production and final recovery or disposal. Waste must be transferred to an authorised person, in other words a person who is either a registered carrier or exempted from registration by the Controlled Waste (Registration of Carriers and Seizure of Vehicles) Regulations 1991. |
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The Environment Agency’s website also contains a guide for Japanese Knotweed remediation called “The Japanese Knotweed Code of Practice”. This offers practical advice on how to decide what is the best treatment program available for different situations. It is not a legal requirement to follow the guidelines but often when dealing with Japanese Knotweed, contractors, consultants and developers will have to liaise directly with the Environment Agency or Local Authorities who will often use it as guidance. The Japanese Knotweed Code of Practice can be downloaded from the following link or by clicking on the button below. LK Group - Japanese Knotweed Information |
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