Japanese Knotweed Removal: Myths, Facts and Guidance for your Garden

Japanese Knotweed is an extremely invasive and competitive plant.

It was brought into the UK in the mid-nineteenth century, as a large ornamental Garden Plant for private gardens & estates, which has now spread all over the UK.

As there are no natural pests in the UK that can combat this plant, due to it being highly invasive and competitive in nature the plant makes it a problem not only for our native wildlife but also for the human environment and related infrastructures.

Once established, Japanese Knotweed is difficult to control.

Japanese Knotweed:
• grows extremely densely and shades out native plants
• provides poor habitats for insects, birds and mammals
• devalues natural landscape
• increases the risk of riverbank erosion when it dies back in the autumn
• creates a potential flood hazard if dead stems fall into watercourses

Japanese Knotweed produces green shoots in early spring which can reach a height of 3 metres before dying back in autumn. The stem can range between 2-3m in height, is green with red or purple specks and forms dense cane-like clumps.

Japanese Knotweed plant if not controlled can create a dense blanket affect choking out other native plant species.

The plant spreads underground by means of creeping rootstalks which can extend 7 metres outwards and reach up to 2 metres deep. Rootstalk fragments as small as 10mm can produce new plants, however, any seeds produced by the plant are sterile.

The Wildlife and Countryside Act 1981 (WCA) provides the primary controls on the release of non-native species into the wild in Great Britain and it is an offence under the act to ‘plant’ or ‘otherwise cause to grow in the wild’ a number of non-native plant species including Japanese Knotweed.

You will not be prosecuted for having Japanese Knotweed growing on your land, however under the Nature Conservation (Scotland) Act 2004, the Scottish National Heritage (SNH) can issue you with a management order, if you are close to or threaten the interest of a SSSI. The main aim of the order is to ensure that the relevant action is being taken to rectify the situation.


Myths & Facts

Myth: Japanese knotweed can grow through concrete & foundations.

Fact: It can’t grow through concrete & foundations, but it can certainly exploit weaknesses such as cracks in concrete, asphalt driveways and drains to appear where it’s not wanted. If you were to build over Japanese Knotweed , it would be unlikely to force its way up through your foundations to emerge in one of your room floors, but it would certainly grow horizontally beneath the house to emerge at the sides and be virtually impossible to eradicate.

Myth : It is illegal to have Japanese Knotweed on your property.

Fact: Although you do not legally need to remove Japanese Knotweed from your land, you may face prosecution if you allow it to spread and grow on to someone else’s land. You can be issued with a management order from the Scottish National Heritage to control the spread of Japanese Knotweed.


If you suspect that you have Japanese Knotweed get it checked out professionally.

Don’t let it get out of control and spread into neighbouring properties.

Get treated by professional contractors as over the counter treatments are not as effective and will take longer to eradicate.

Treatment Methods

Spraying: Spraying with chemicals (herbicides) is an effective method of treatment to stop the spreading of the plant. This can’t be carried out when it’s raining or in windy conditions and has the potential of affecting other plants and soil.

Stem injection: This method of treatment where the herbicide is directly injected into the lower part of the mature stems using an injection gun. This method can be carried out in most weather conditions unlike the spraying method. As this method is to inject the plant it can be an environmentally friendly method of control, you will not have to worry about the chemicals used spilling into any watercourses or causing damage to any protected species/trees nearby because the measured does go directly into the stems.

Burning method: This method is used when the plant has died back, burning away the weed has the benefit of not contaminating any other soil or plants. You will require to dig up all the root system and may require more than one treatment as the root system can be 7 metres long and 2 metres deep and it is imperative that all the roots are destroyed to eradicate the weed.


Protecting Your Garden

Identify possible route of contamination.

Check out the surrounding area for other outbreaks.

Knotweed can choke out other plants.

It can displace patio slabs, mono-block and stone walls.

An effective treatment programme should be put in place to control the spread and eventual eradication which will take over 3 to 5 years of continuous treatment and monitoring.

WCC West Coast Group Ltd have certified staff that offer treatments to control and eradicate this highly invasive weed. Contact us today to find out how we can remove Japanese Knotweed from your property.