Japanese Knotweed Survey
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Japanese Knotweed Survey

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Japanese knotweed infestation

Japanese knotweed infestation


Japanese Knotweed Spread and Survey  

tel: 0333 456 7070
mob: 07950 259 905


In the UK Japanese knotweed has not yet been recorded as producing viable seeds, however, hybrid crosses can produce viable seed. So far all Japanese knotweed plants recorded in the UK are female and all male plants have been shown to be hybrids. Fertile hybrids will add a whole new dimension to the control of the spread of Japanese knotweed which currently only reproduces vegetatively.

The plant does have an extraordinary ability to spread vegetatively from crown, stem and rhizome (underground root). Even tiny amounts of cut stem, crown or rhizome are capable of producing a new plant. Controlling spread is therefore dependent on preventing the spread of stem, crown and rhizome. Rhizomes grow rapidly underground and are responsible for the spread of the plant on site. They produce long white shoots at the apices of the rhizome, which send up shoots to the surface.

If the rhizome is cut it will produce a shoot, therefore digging or other disturbance is known to increase stem density. If soil contaminated with rhizome is moved to another part of the site or to another site it will re-grow and cause spread. Rhizome is particularly resistant to dehydration and freezing. As little as 10 mm or 0.7 gm of rhizome can regenerate into a new plant. Crown and stems are also capable of regenerating and even small fragments of cut crown or stem are capable of regenerating and becoming a new plant. If the plants are cut back it is important to dispose of the crown and stems properly, usually by burning. Once stems are thoroughly dried they are unable to regenerate.

Preventing spread

It is important that an effective Japanese knotweed management programme is established including, where possible, herbicide treatment, otherwise the plant will inevitably spread. All cut or pulled stems of Japanese knotweed should be treated with extreme care as they can potentially re-sprout and cause spread. They should be kept on site, or disposed of in a licensed landfill site that can carry out deep burial (by prior arrangement) to prevent spread onto other sites. Treatment of colonies on riverbanks should be treated as soon as possible because bank erosion can lead to plant material breaking off and dispersing downstream.

As stems, crowns and rhizomes readily regenerate, they must be allowed to dry out thoroughly after they have been pulled or cut, this can be helped by putting the material onto a plastic sheet rather than on the ground. Regular checks should be made to ensure that this material is not contaminating watercourses or other sites, or developing roots. Thoroughly burning plant material on site after cutting and drying, where current by-laws allow, can be an effective means of disposal provided that the waste is burnt on site and not removed to other land.

Ensure that machinery, tools and work clothes are free of fragments of knotweed before leaving the site. Tracked vehicles, off-road tyres, tools and even work boots can harbour fragments of knotweed and could potentially cause spread to another site. These items should be thoroughly cleaned before leaving a knotweed-contaminated site. Japanese knotweed material is regarded as ‘controlled waste’ and not disposing of it properly would be an offence under the Environmental Protection Act, 1990. Allowing the spread of Japanese knotweed into the wild is also an offence under the Wildlife and Countryside Act 1981.

Survey and Management

Once you find Japanese knotweed on a site, it is essential that you set up some form of Japanese knotweed management plan (KMP). You need to appoint a suitably qualified and experienced survey company to visit the site and mark and map the extent of the Japanese knotweed on the site and to identify a clerk of works to oversee the management plan which is produced. You need to let all relevant contractors on the site know how important the plan is, for example through ‘toolbox’ briefings to staff operating on the site. It is important to only disturb a minimum amount of Japanese knotweed and it is vital that you keep this contaminated material separate from other waste and surplus soil within the site. Soil free from Japanese knotweed and other waste may be disposed of relatively cheaply under exemptions from waste licence. Unless an area of Japanese knotweed is likely to have a direct impact on the development, you should control it in its original location with herbicide over a suitable period of time, usually two - five years.

The Knotweed Management Plan is an important document and provides a valuable record of the treatment of the site for future owners. It may also provide evidence that the site has been appropriately managed if subsequent Japanese knotweed re-growth results in litigation against the contractor.

> Identification Service

Not sure if it is Japanese knotweed? Email photographs for our surveyor's expert opinion.

We can also send a surveyor's letter identifying the plant in the photographs if required.
*fees and conditions apply

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Company’s Registered Office Address: 597 Etruria Rd, Basford, Stoke On Trent, Staffordshire. ST4 6HP.
Japanese Knotweed Survey © Copyright 2011

Japanese knotweed survey, management, control, eradication & land remediation relief.
Areas include Staffordshire, Cheshire, West Midlands, Manchester, Birmingham & Stoke On Trent.

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