Japanese knotweed

Japanese knotweed has spread with vigour throughout the United Kingdom since its introduction as an ornamental plant in the 19th century.

There is a wide variety of conditions in which the plant can survive including areas of volcanic activity and this is often the first plant life to grow after an eruption. This demonstrates its sheer robustness and helps us to understand why Japanese knotweed eradication is notoriously difficult.

The UK strand of the plant has developed to exaggerate its normal adaptability. It now grows at an exceptional pace of up to 10cm per day in areas of varying conditions. The plant is easily spread from the smallest fragment and human interference, birds and weather are the main culprits where movement of the plant is concerned.

The spread of Japanese knotweed throughout the United Kingdom has not been restricted by geographical area; it has been sighted from Cornwall to the Scottish Highlands, as well as Wales and Northern Ireland. Both rural and urban areas are affected, making Japanese knotweed removal more essential than ever. The weed can inhabit contaminated land, development sites, and landfills sites. There are now strict regulations for Japanese knotweed removal, disposal and its introduction to the landfill sites as it is classed as controlled waste.

Identification of knotweed

There are a number of ways to identify Japanese knotweed, although, like any other plant, its shape, size and colouring can vary dramatically.

LEAVES

Colour - Young shoots have curled-up red/purple or light green leaves with red/purple colouring. They become ‘Lush green’ when mature in the growing season. During autumn/early winter they turn yellow/brown.
Shape - Can be described as heart- or shield-shaped; broadly oval to somewhat triangular.
Size - Up to 22cm in length and roughly 2/3 as wide.

FLOWERS

Appearance - 80mm-120mm long clusters of small green-white flowers, blooming from late summer to early autumn.

STEMS

Appearance - Bamboo-like, regular, swollen and often red joints, nodes or knots.
Colour - Red and asparagus-like when a young shoot. Stems develop throughout the growing season from being supple and green to brown and brittle. Stems sometimes have characteristic red/purple specks or spots.
Size - Up to 4cm in diameter. Stems grow up to and over 3m in height.
Structure – Hollow stems with periodic nodes. Snap a stem off to test this.

Eradication strategies

The HIT® (Holistic Integrated Treatment) family of systems provides the land owner or developer with a variety of sustainable and environmentally sound choices for Japanese knotweed eradication.

Following our initial survey, solutions for your site are designed around your development plans and to suit your budget and time scales and could use one or a combination of the techniques described below.

We specialise in developing an eradication programme that will have minimum impact on the site’s development, even when Japanese knotweed is identified at a critical point of the project plan.

Environmentally Sensitive Areas

Eradication methodologies can be tailored to suit the most environmentally sensitive areas found, including sites adjacent to watercourses, Sites of Special Scientific Interest (SSSI), Areas of Outstanding Natural Beauty, woodlands and other areas deemed ecologically sensitive because they contain protected flora and fauna.

With input from our in-house BASIS qualified advisor and our full time ecologists, we can develop an eradication strategy that will take two years to complete. All works in environmentally sensitive areas are undertaken with the full approval of the local Environment Agency office and include consultation with Natural England and the Wildlife Trusts when necessary.

Integrated On Site Treatment

This method involves the excavation and removal of Japanese knotweed from the area of the site required for immediate development, and moved to a more convenient area of the same site. The spoil can then be stockpiled, allowing the Japanese knotweed to re-grow sufficiently, without further contaminating site soil, so that herbicidal treatment will prove effective the following growing season. The HIT® system is then used to treat the stockpile, and once eradication has been judged successful, the soil will need to remain in-situ. If the treated soil is to leave site, it will be classified as controlled waste and have to be disposed of accordingly.

This method of eradication can often complement development plans, but also saves money, is sustainable, and reduces the environmental impact of the eradication process when compared to ‘dig and dump’.

Soil Screening

Soil screening is a sustainable, time efficient and effective method of separating Japanese knotweed from soil following excavation. It is the most preferred method for customers who want minimal environmental impact combined with quick results.

Soil is passed through a variety of screening processes after which spoil can be transported to licensed land fill, incinerated on site or taken to a biomass power station for use as fuel. The remaining soil can be reincorporated on the site, eliminating the need to import large quantities of back fill.

Soil screening uses large plant making it a suitable application for use on sites that are in excess of 1,000m². TCM Ltd have recently introduced a mini screener allowing us to use this treatment method on much smaller sites such as residential properties.

The method requires supervision by trained specialists but gives the fast turnaround of ‘dig and dump’. We hold a Mobile Treatment Licence and have WAMITAB qualified staff.

On Site Burial and Cell Encapsulation

Where space is at a premium on a site and only a short time frame is available, on site burial or cell encapsulation can be options to pursue. Sub strata soil conditions such as water table level and soil type need to be assessed to determine which the best option is. When onsite burial is recommended, one treatment with a non-persistent herbicide should be applied in order to reduce the vigour of Japanese knotweed. A pit needs to be dug to a depth of 5 metres. The Japanese knotweed is then excavated under the supervision of our staff, using our reduced excavation methodology, and transferred to the pit. The spoil is then covered with membrane and the pit is filled in.

When cell encapsulation is recommended, a pit is dug to a depth of 2m and the pit is then lined with a heat joined membrane. The Japanese knotweed is excavated under the supervision of our experienced staff using our reduced excavation methodology and transferred to the pit. Further heat joined membrane is then laid on top of the spoil and the edges are sealed. The remainder of the pit is then filled in.

This option is only suitable where there is no likelihood of future excavation over the burial area. The location of the pit must be mapped clearly and this information must be stored.

Reduced Excavation

Our reduced excavation methodology can offer cost effective project management. Reduced excavation must be supervised by trained specialists and involves reducing the quantity of material for disposal to landfill via detailed monitoring, followed up by post excavation herbicidal treatment. This method can also be backed up by warranty, and can also result in savings of around 50% when compared to the Environment Agency’s guidelines where all soil contained within a radius of 7 metres and to a depth of 3 metres is removed.

Off Site Disposal

When there are time or space constraints, sometimes off site disposal is the only option for the developer. Using our reduced excavation method, up to 50% less spoil than the Environment Agency’s guideline recommendation needs to be transported to landfill, making this a more sustainable and cost efficient option for our customers.

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  • We are experts in removing japanese knotweed
    through proven scientific methods.

    We are experts in removing japanese knotweed through proven scientific methods.