Guidance on the control of Japanese Knotweed

What is Japanese Knotweed?

Japanese knotweed fallopia japonica as the name implies is a native plant of Japan, Taiwan and Northern China. It was first introduced to the UK in the early 1800s as an ornamental plant.

What does it look like?

Japanese knotweed is a vigorous perennial plant that can grow in excess of three metres in height and is commonly seen on riverbanks and wasteground. When Japanese knotweed colonises areas, the plant forms dense thickets that die back to dead, rigid stems in the winter, only to re-grow more vigorously the following growing season.

Why is Japanese knotweed a problem?

In the UK, Japanese knotweed has no natural predators or controls. Consequently it has been able to colonise areas throughout the British Isles. The lack of natural controls has resulted in a number of problems including shading out other native species, the accumulation of litter amongst the stems, riverside erosion when knotweed dies back and damage to pavements, buildings and car parks as knotweed is able to grow through asphalt.

Japanese knotweed grows vegetatively, spreading by means of underground stems or rhizomes that push through the soil and put up areial shoots periodically. When broken off, very small fragments of rhizome (as little as 2.5cm/1 inch in length) can form new plants. Rhizome fragments are also viable for a long period of time. For these reasons, and since Japanese knotweed has no particular habitat preferences in the UK, this plant is a major problem.

Is it an offence to allow Japanese knotweed to grow in the wild?

Japanese knotweed has a number of closely related sub species which also form hybrids, all of which come under the provisions of the Wildlife and Countryside Act (1981) which states that 'it is an offence to plant or otherwise cause the plant to grow in the wild.' Furthermore, the Environmental Protection Act (1990) classes Japanese knotweed as 'controlled waste' and consequently should be disposed of at a licensed landfill site under the EPA (Duty of Care) Regulations (1991).

How can I control Japanese knotweed?

There are various approaches used to control Japanese knotweed. Primarily these comprise spraying and cutting or a combination of both. Where appropriate, grazing may also be a management option. Another alternative is covering the Japanese knotweed with a membrane and over-planting with a quick growing species such as willow.

How can I control Japanese knotweed on my land?

If Japanese knotweed is regularly pulled up or cut, the plant is weakened and over a number of years will begin to die off. If feasible, a good way of disposing of the plant once pulled or cut is to thoroughly burn it. However, unless you intend to take the plant remains to a licensed landfill site, the Japanese knotweed must be kept on site, otherwise a breach of the above legislation will have occurred.

Another alternative is to apply a herbicide. One of the most common herbicide applications for the control of Japanese knotweed and other invasive plants such as Himalayan balsam, is a herbicide that contains glyphosate as an active ingredient. Glyphosate is what is known as a non-specific herbicide, which means it will affect most plants to which it is applied. Therefore, care must be taken when applying glyphosate based herbicides if the treatment is close to sensitive areas. Glyphosate used for domestic use can be purchased from garden centres and retailers under a number of names including Roundup, Tumbleweed and Tough Weed Gun.

The effectiveness of the herbicide is dependent on the amount of Japanese knotweed that needs to be treated. If you wish to treat large stands of Japanese knotweed you may wish to consult a contractor. If you consider that the area of Japanese knotweed that needs treating is manageable, you may wish to consider a combination of cutting and spraying in early summer followed by spraying again in late summer.

Whichever management approach is decided upon, regular monitoring of the area should be undertaken to ensure the knotweed is not spreading elsewhere or contaminating watercourses.

Where can I dispose of Japanese Knotweed?

Japanese knotweed and soil containing Japanese knotweed is classed as 'controlled waste' under the legislation referred to above. This means it can only be disposed of at licensed landfill sites. The nearest waste disposal site licensed to accept Japanese knotweed is:

Biffa Waste Services, Trecatti Landfill Site, Fochriw, Nr Dowlais, Merthyr Tydfil, CF48 4AB

Telephone no. - 01685 721882 / Fax no. - 01685 387285.

• Will need a minimum of 24 hours notice to arrange disposal.
• Minimum charge of 3 tonnes plus a proportion of the landfill tax depending on weight.
• Trailers to be covered during transit with small quantities to be securely bagged up, not loose, and drivers to ensure vehicle is empty and clean before leaving site.

What other factors in relation to Japanese Knotweed should I be aware of?

• The Vale of Glamorgan Council and Environment Agency Wales are not obliged to control Japanese knotweed  on behalf of other landowners.
• It is the landowner's responsibility to control Japanese knotweed on their land if it is affecting neighbouring land.
• If treating Japanese knotweed near watercourses, the Environment Agency Wales will need to be contacted on 08459 333 111.
• The persistence of Japanese knotweed rhizomes makes the plant hard to eradicate. Therefore, be aware that you will need to treat Japanese knotweed for a number of years, even though you may think you have killed it after the first treatment.
• Early identification and treatment of Japanese knotweed will save money and time in the long term as the plant is only beginning to establish and will be less vigorous compared with when it is established.
• Licensed Japanese knotweed sprayers must have a current National Proficiency Test Certificate. For knapsack spraying these certificates are PA1 and PA6 or equivalent.
• Mowing and flailing Japanese knotweed will cause it to spread.
• Do not compost or chip Japanese knotweed.

Who can I contact for more information?

If Japanese knotweed is growing on Council land in the Vale of Glamorgan please contact the Council's C1V call centre on 01446 700111.

When growing near a watercourse or river contact the Environment Agency Wales on 08459 333 111.