Japanese knotweed

Please do not dispose of Japanese knotweed with normal household waste or your green bin

 What to do if you find Japanese knotweed on your property

  • Do not allow it to become established - if you have Japanese knotweed on your property treat it immediately
  • Do not fly-tip Japanese knotweed, or any other garden waste
  • Do not dispose of Japanese knotweed with normal household waste
  • Do not contaminate green waste bins with knotweed material
  • Do not compost knotweed
  • Do not flail, mow or cut Japanese knotweed, as this will cause it to spread. Flailing of dead stems after herbicide treatment and complete dieback, or in winter months, is acceptable
  • Do not spread Japanese knotweed stems and crowns. All material removed must be safely contained and disposed of at a licensed disposal site. The landfill operator must be notified that you are disposing of Japanese knotweed 
  • Do not spread soil contaminated with Japanese knotweed rhizomes (root system). Any soil that is obtained from ground within seven metres of a plant could contain rhizomes
  • Do not chip or shred Japanese knotweed. Mechanical chippers do not kill this plant. If you spread any chipped or shredded material knotweed can re-grow from tiny pieces of the plant

What is Japanese knotweed?

Japanese knotweed (Fallopia japonica) is a perennial plant brought into the UK as an ornamental garden plant in the 1800’s. It is the most invasive plant/weed in Britain.

Japanese knotweed is listed under Schedule 9, Section 14 of the Wildlife and Countryside Act 1981.

It is an offence under this act to plant or otherwise cause the species to grow in the wild. Allowing Japanese Knotweed to grow over the boundary of your property can be classed as allowing the species to grow in the wild and would be an offence under the Act, leaving you liable to prosecution. Failure to control this species may result in enforcement action by the Environment Agency.

Japanese knotweed is a weed problem that can be successfully treated with herbicides, although it may take several applications to eradicate.

What does Japanese knotweed look like?

  • Japanese knotweed has bamboo like stems and green oval shaped leaves with a distinctive zig zag pattern, in early spring red or purple shoots will grow from the stem
  • white flowers appear on the stems in late summer
  • in autumn the leaves and flowers will turn brown and fall off. Dead stems can remain for up to 3 years before decomposing
  • Japanese knotweed spreads very easily and will grow wherever it lands. It has even been known to grow up through floorboards into living rooms

Herbicidal control

There are several herbicides available for use on Japanese knotweed. The choice of herbicide will be dictated by the situation the weed is growing in.

TORDON 22K - Picloram  
This product acts through foliage and the roots, has a residual activity for up to two years and does not kill grasses. The disadvantage with this product is that it cannot be used near watercourses or under tress that you wish to retain, as it can be absorbed into the root system and will kill mature trees. 

ROUNDUP Pro Biactive/Pro green – Glyphosate
This acts through the foliage and is trans-located through the root system. This product will kill all vegetation including grasses, and has the added benefit that it can be applied in or near watercourses. The product cannot be absorbed via root systems and it is broken down on contact with soil. Depending on the time of the first application you may need to spray two or three times to ensure knotweed is killed off.

GARLON/TIMBREL – Tryclopyr
This is a selective herbicide, rapidly absorbed through foliage and roots. Grasses are not affected at normal dosage rates. Again, the use of these products is not permitted near watercourses.

It is essential that you comply with the recommendations on the product labels. If you have any concerns over the use of these products please check with the manufacturer.

Last updated: 20 December 2016 12:07:30