Japanese Knotweed is a harmful weed, which if left ignored, will effect other species of plants and can cause extensive damage to property. Under the Wildlife and Countryside Act 1981, causing the plant to spread is an offence.
The plant is extremely difficult to get rid of; attempts to control the weed often fail and re-growth occurs. It is very important not to do anything that may help the knotweed to spread. In particular transporting any part of the plant to another site may produce other infestations and may leave you liable to prosecution. The plant can grow through tarmac roads, between joints and cracks in concrete slabs, within cavity walls and drains.
What does it look like?
It is green with heart or oval shaped leaves approximately 10 - 15cm wide. Stems are green, hollow and jointed, similar to bamboo and may have purple or red specks. Roots are knotty and brown, although when broken they are yellow, orange or red. Between August and October small white flowers appear in clusters on the tips of most stems. In the winter the plant dies fully back to ground level leaving dead, dry plants and stems on the surface. Regrowth in the spring is very rapid with the plant quickly attaining a height in excess of 1.2m
What to do if you find a noxious weed?
Do not
- Wave as this may cause it to spread through seed spreading
- Spread the stem and crowns
- Try to dig up as this will lead to a significant increase in stem density
- Spread soil if contaminated with Japanese Knotweed
- Take Japanese Knotweed to recycling centres that receive garden waste as it will contaminate the compost
You should:
- Positively identify the plant before taking action If cutting down is recommended, cutting with hand tools or hand pulling is best.
- Dispose of it on site. Materials taken off site must be safely contained and disposed of at a licensed disposal site. Burning of all parts is a good option.
- Follow the Environment Agency's Code of Practice for the weed involved.
- Handle weed killer (herbicides) safely and effectively. Make sure you get the approval of the Environment Agency prior to treatment if you intend to use a herbicide in or near water.
- Spraying should be performed during still, cool dry conditions, without rain for 6 hours.
- Compost the knotweed separately (preferably on plastic sheeting to prevent rooting) so that you can be sure it is dead before you apply it to land.
If you find it on your property it should be treated on site to minimise the risk of spreading. For further information please contact the Environment Agency on 08708-506506 or visit the website www.environment-agency.gov.uk