Japanese knotweed is a perennial non-native plant from the knotweed family which is subject to certain Government legislation due to the speed and spread of its growth choking other plants in its path.

Find out all you need to know about the plant – and how to spot if you have it in your garden – in our article Everything you need to know about Japanese knotweed.

If you have identified Japanese knotweed in your garden and want to get rid of it, here’s what you need to know.

Why do I need to get rid of Japanese knotweed?

If you have Japanese knotweed in your garden, you will probably want to control its growth and spread so that it doesn’t either damage your property or spread into areas which you don’t own. If the plant spreads from your property into the wild, then that is illegal according to the Wildlife and Countryside Act 1981. If the plant spreads on to someone else’s property or public land and you don’t actively work to control its spread, you could be subject to an ASBO and fined. 

How to get rid of Japanese knotweed

There are a number of ways to tackle Japanese knotweed:

Digging it up 

This can work, but because the root systems are so extensive (up to 22ft) and because the plant spreads by rhizomes – underground shoots – this is not an ideal solution. Regrowth will often occur.

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If you do choose this method, there are some important things to consider. Any waste you have which contains Japanese knotweed must be disposed of properly. It can only be removed to a landfill site which has an appropriate permit. Furthermore, it can only be taken to the landfill by a specialised registered carrier, whose vehicle must be thoroughly cleaned after use.

You should never compost waste containing Japanese knotweed because it can survive the composting process. It must not be disposed of with the normal household was as it is a contaminant.

Japanese knotweed

It is possible to burn the Japanese knotweed waste on your land after letting it dry out first, but Japanese knotweed rhizomes may still survive the burning process, so you will still need to have any burnt waste transported to the specialist landfill as above.

Farmers burning Japanese knotweed plant waste have further legal obligations to follow.

For more information about the proper disposal of Japanese knotweed waste, check out Environment Agency guidance.

Chemical treatment

Many people oppose using chemicals to treat weeds and plants in the garden. However, with a plant as tenacious as Japanese knotweed, it is the safest, most-recommended option.

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When using weed-killers or root-killers, make sure you only use approved chemicals. Always follow the manufacturer’s instructions.

The Royal Horticultural Society recommends using a glyphosate-based weed-killer to tackle Japanese knotweed, particularly Scotts Roundup Tree Stump and Root Killer.

You should cut back the plant stems before applying.

It can take three years to fully treat Japanese knotweed, so plants will have to be resprayed every year. Try to avoid any other plants when you spray.  

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Get the professionals in

There are many companies offering their services to dispose of Japanese knotweed. Check out the British Association of Landscape Industries website, as recommended by the Royal Horticultural Society, for a list of its members who treat invasive species.

Photo credits: FLPA / Paul Miguel/REX/Shutterstock, FLPA/REX/Shutterstock