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Plants

Japanese Knotweed

Japanese knotweed

Japanese Knotweed (Fallopia Japonica) is an attractive but rapidly, fast growing plant.

Under no circumstances should Japanese Knotweed be disposed of in your green garden or blue recycling bins. Please use a specialist contractor.

In winter the plant goes beneath the ground but by early summer the bamboo-like stems shoot to over 2.1m (7ft). Removing the plant is very difficult whether it's through hand or chemicals. The plant suppresses all other growth and can affect both wall and building foundations.

While the plant is not illegal new legislation around Japanese Knotweed was introduced by the Government.

What's the problem with Japanese knotweed?

Japanese knotweed is not unattractive but its rapid, strong-growing annual growth and relentless speed allows it to easily overwhelm other garden plants. The plant does not produce seeds, it sprouts from very small sections of rhizomes. The plant can disrupt walls, pavements and foundations. Under the Wildlife and Countryside Act 1981 it is an offence to cause Japanese knotweed to grow in the wild.

New legislation

An amendment to the Anti-Social Behaviour, Crime and Policing Act 2014 includes a section on Japanese knotweed and other invasive non-native plants including the Himalayan balsam and Giant hogweed. The legislation identifies:

  • On your property you should aim to control these plants and prevent them from becoming a problem in your area. If they have a 'detrimental effect of a persistent or continuing nature on the quality of life of those in the locality', the legislation could be used to enforce its control.
  • Control can be carried out by the homeowner and doesn't require a specialist company. However, a specialist company will be skilled at control and can dispose of the plant waste.
  • Identification is important. Japanese knotweed can sometimes be confused with other plants including the Persicaria micrcephala 'Red Dragon', Leycestria Formosa and Houttuynia cordata (see below images).
  • Where problems with Japanese knotweed occur in neighbouring gardens, we suggest that you speak or correspond directly with your neighbours (who may already be taking action to control this difficult weed). These informal steps should be taken before contacting the council.

How to control Japanese knotweed?

Non-chemical
All weeds can be controlled without weed killer, but Japanese knotweed is persistent and deep rooted which is very difficult to eradicate.

  • Digging: Due to the depth, regrowth usually occurs. This method also causes disposal problems. Under the Environmental Protection Act 1990 disposal can only take place at licensed landfill sites. Specialist Japanese knotweed contractors are licensed to safely remove the weed.
  • If digging out is attempted, remove as much root as possible, then repeatedly destroy re growth. This process may take several seasons.

Chemical
Glyphosate

  • Most effective and simplest method is when Glyphosate is applied to the foliage which is then passed to the underground parts. The best time for spraying is around May when the weed is 90cm (3ft) and then a reapplication in late summer.
  • Glyphosate-treated knotweed will often produce small-leaved bushy re growth the following spring. This is very different in appearance to the normal plant and is essential that the re growth is treated immediately.

Other forms of Glyphosate include Scotts Roundup Ultra 3000, Scotts Tumblewood, Bayer Tough Rootkill or Doff Maxi Strength Glyphosate Weedkiller. 

Giant Hogweed

Giant Hogweed

Giant hogweed (Heracleum mantegazzianum) is an attractive, invasive plant with sap that can cause severe skin burns.

Do not place giant hogweed into the green garden or blue recycling bin. To dispose please use a specialist contractor.

The tall plant can reach over 3.5m (11.5ft) or more with flower heads as large as 60cm (2ft) across. The cow-parsley like plant can look attractive with thick often purple-blotched bustle stems.

While the plant is not illegal and there is no statutory obligation for home owners to eliminate giant hogweed Central Government introduced legislation to help control the weed.

What's the problem with Giant hogweed?

Giant hogweed is invasive and potentially harmful. Chemicals in the sap can cause photodermatitis or photosensitivity, where the skin becomes very sensitive to sunlight and may suffer blistering, pigmentation and long-lasting scars.

While this is one of the species, there are as many as four other giant hogweeds at large in Britain some of which are biennial and others perennial. However, when tested all of these had high levels of furanocoumarins (the chemicals which cause burning by making the skin sensitive to sunlight) and so all pose a risk to public health. There is also a native hogweed, Heracleum sphondylium, which will be a familiar plant to gardeners and those who like walking in the UK. It can grow to 6 foot or so when in flower and can cause rashes and other skin complaints but reactions tend to not be as severe as with larger species.

Legislation

Giant hogweed has been applied to legislation within the Countryside Act 1981 and lists the plant under Schedule 9, Section 14 meaning it is an offence to cause giant hogweed to grow in the wild of England and Wales. The weeds can be subject to Anti-Social Behaviour Orders where occupiers of giant hogweed infested ground can be required to remove the weed or face penalties.

How to control giant hogweed?

When controlling giant hogweed always wear gloves, cover your arms and legs, and ideally wear a face mask when working on or near it (this is so a strimmer will not cut the sap and it hits your face). Cut plant debris, contaminated clothing and tools are potentially hazardous too. Wash any skin that comes in contact with the plant immediately. Ensure any contractors working on your land are aware of the risks.

Non-chemical

  • If in a garden pull up plants by hand when the soil is moist. Do this in May when the plant hogweed has reached a reasonable height, but before it has produced its flowering spike.
  • Never let hogweed set seed, but allow the flower spike to form and then remove it before the flowers fades.
  • Larger scale areas - leave to a specialist contractor

Chemical

  • Weedkiller based on glyphosate is usually the best choice as this will also kill roots. Giant hogweed prefers moist fertile area often near waterways. Seek advice from the Environment Agency before undertaking spraying near rivers, streams and ponds.

Himalayan Balsam

Himalayan Balsam

Himalayan balsam (Impatiens glandulifera) grows rapidly and spreads quickly, smothering other vegetation as it goes.

Under no circumstances should Himalayan balsam be disposed of in your green garden or blue recycling bins.

Between June and October it produces clusters of purplish pink (or rarely white) helmet-shaped flowers. The Himalayan reaches well over head height at 2-3m (6-10ft)and is a major weed problem especially on riverbanks, waste banks and gardens.

What's the problem with the Himalayan balsam?

Each plant can produce up to 800 seeds. These are dispersed widely as the ripe seedpods shoot their seeds up to 7m (22ft) away. Himalayan balsam tolerates low light and shades out other vegetation, so gradually impoverishing habitats by killing off other plants. It is sometimes seen in gardens, either uninvited or grown deliberately, but care must be taken that it does not escape into the wild.

Once established the weed is extremely difficult to remove and it may take several seasons to obtain good control.

How to control Himalayan balsam?

Non-chemical
Himalayan balsam can be pulled and cut as long as this happens before they flower and set seed. This may need on-going control as it can be difficult to eradicate.

  • Hoeing: Run a howe over a bed or between rows to kill seedlings. Choose a dry day with light wind, so the seedlings will dry out on the surface of the bed rather than re-rooting into moist soil.
  • Hand-pulling or hand-weeding with a fork: Pull up before they set seed or dig up and remove as much root and bulb as possible. Hand weeding is easiest on lighter soils and should only be attempted where it will not disturb the roots of garden plants.
  • Root barriers: Insert into the soil to stop the spread of weeds and restrict invasive plants.

Chemical

  • Choose a weedkiller that is most appropriate for the purpose by reading the label before buying or using. Contact weedkillers and glyphosate have low persistence in the soil, being virtually inactivated on soil contact. Residual weedkillers persist in the soil for several weeks or months and can move deeper or sideways in the soil, leading to possible damage or underlying plant roots.

Before using weedkillers alongside waterways it is necessary to contact the Environment Agency.

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