Root Barriers

Japanese Knotweed is a strong growing herbaceous plant native to Japan, Taiwan, China, and the Korean peninsula. It was introduced into Europe in the mid-19th Century as an ornamental plant. The plant has thrived in fertile European soils and is now classified as an aggressive weed species. In order to protect structures and avoid the spread of this and other invasive plant species and effective root barrier should be specified.  

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Cutex Root Barrier for control of Japanese Knotweed

You must do both of the following to control specific plants:

  • prevent invasive non-native plants on your land from spreading into the wild and causing a nuisance
  • prevent harmful weeds on your land from spreading on to a neighbour’s property

It’s important that you can identify them so you can control them in the most appropriate way.
Although Japanese Knotweed is considered to be the most aggressive of invasive plant species, other plants are also grouped within this category. The legislation views these other species with the same level of importance.

Japanese knotweed affects both natural and man-made habitats. It is particularly well suited to riparian areas, which allows the dispersal of fragments of the plant downstream where new colonies can also form. It is also found colonising man-made habitats such as roadsides, railways and brownfield land. The plant is primarily spread through rhizome fragments. Even fragments less than 1g in weight are considered viable and could potentially form a new knotweed colony. As well as movement in water, the plant can be dispersed through garden waste, fly-tipping and machine at construction sites. In established colonies, the rhizome can extend up to 7m. The plants are typically 2-3m in height with mature leaves up to 120mm in length.

The large size of the plant results in a significant visual impact on the environment where it occurs. It also can present considerable damage to the affected area. Japanese knotweeds stout rhizomes can push through asphalt, building foundations, concrete retaining walls and even drains. It out-competes other species which affects landscaping programmes affects the aesthetics by accumulation of litter in dense thickets which encourages vermin, increases the maintenance costs of buildings and the large infestation if a non-native plants along rivers, hedges and railways can also disturb local ecosystems by blocking migration of native plants and animals. This can add huge costs to development and regeneration schemes. Contaminated soil must be treated as controlled waste. Additionally, knotweed is capable of obscuring railway signals and road signs as well as causing trip hazards in paving. Hence, Japanese Knotweed can cause excessive costs for remediation, prosecution and/or compensation claims, especially from neighbouring sites, physical damage to buildings and hard surfaces and harm to the environment (through the repeated applications of herbicides).

As a consequence, legislation exists to prohibit its further spread. For example, in the UK it is an offence to plant or otherwise cause Japanese knotweed to grow in the wild or to spread under the UK Wildlife and Countryside act 1981. Under the UK Environmental Protection Act 1990, Knotweed plant material is classified as a controlled waste.

It is not illegal to have Japanese Knotweed on your land, however legislation requires that you:

  • prevent invasive non-native plants on your land from spreading into the wild and causing a nuisance
  • prevent harmful weeds on your land from spreading on to a neighbour’s property
  • You can be fined up to £5,000 or be sent to prison for up to 2 years if they allow contaminated soil or plant material from any waste you transfer to spread into the wild.

CuTex Root Barrier

Cutex is a geocomposite root barrier system consisting of a copper sheet mechanically encapsulated within a woven polypropylene geotextile and a high strength nonwoven polypropylene geotextile. The copper acts as a signal layer that all plants avert their growth from. The copper foil only releases minute quantities of the copper ion. These do not constitute an ecosystem burden, or impact on groundwater.

Plant shoot/root primordia (growth tips) are averse to growing into the vicinity of copper concentrations. In essence, the roots/shoots turn their growth in a different direction when confronted with the copper foil. These principles make CuTex a suitable barrier for Japanese Knotweed growth as well as all other plants. The majority of the Japanese Knotweed rhizome exists in the upper layers of topsoil. It has been established that, in an infected area, 14,000kg/ha dry weight of Knotweed may exist in the top 250mm (Brock, 1994).

CuTex geocomposite can provide a direct protection of utilities’ infrastructures such as foundations and drains from root intrusion, landfill caps and ‘green’ roofs. It will also provide a protection to roads, railways and dams.

Japanese knotweed root barrier
Soil layers binded together by the roots (left) vs sample where CuTex was used: roots where confined in the top layer (right).
Japanese knotweed root barrier
Confocal laser scanning microscopy (CLSM) image of healthy root (left) vs inhibition effect of CuTex, that caused the root cells to collapse (right).

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