Identifying Japanese knotweed

The time of year really determines what you need to look out for when identifying Japanese Knotweed.

Our handy guide below should give you a better idea to identify Japanese knotweed and then determine whether or not your need to think about Japanese knotweed treatment.

 

Identifying Japanese knotweed in spring

In spring new shoots red/purple in colour begin to appear and look not unlike asparagus spears. As the canes grow, leaves begin to unroll and the plant turns green. Growth is rapid and mature canes can reach 3 metres (10 feet) in height. The mature canes are hollow and have a characteristic pattern of purple speckles. The leaves are carried on stems in a distinctive zig zag pattern

 

Identifying Japanese Knotweed in summer

In summer, Japanese knotweed growth is almost exponential with a height of 2-3 meters. The density of the plant can be seen at this stage. The stems now have their bamboo like appearance and just like bamboo are hollow. They are now green with red specks and leafs on the stems growing in a zig-zag pattern. The leaves also have quite a distinctive shape with a pointed tip and a straightened edge. Between August and October the plant will have its tiny white flowers.

Identifying Japanese Knotweed in winter

During late Autumn/Winter, the canes die off and the plant becomes dormant. Shoots may however, be visible for the new growing season. The canes lose their leaves and turn dark brown/red in colour. The dead canes remain standing and may take up to 3 years to decompose. Much of the litter may remain from previous seasons causing piles of dead canes that suppress competition from native flora and garden plants.

 

Further information for identifying Japanese knotweed

Early infestations of Japanese knotweed rarely achieve the height associated with mature stands. Canes produced from encroaching knotweed, or growth from small pieces of the plant material, tend to form short canes until the rhizome becomes established. Early treatment of new Japanese knotweed infestations when they are still immature is highly recommended.  View the video to the left to see how fast and how damaging Japanese knotweed can be.

Still unsure with identifying Japanese knotweed?

If you are still unsure whether or not you have a Japanese knotweed issue and you want to speak to an expert, simply contact us online, find your local branch or call 0800 65 20 376 and speak to one of our Japanese knotweed specialist to help you identify if you have an issue

Alternative, book a Japanese knotweed survey.

More information on Japanese knotweed

For further information on Japanese knotweed, check out the web pages below:

	Japanese knotweed identification and control guide Download our Japanese knotweed control and identification guide for help and advice towards a Japanese knotweed issue.   Identification and control guide
	Japanese knotweed treatment Find out how to treat Japanese knotweed on your property. Japanese knotweed treatment
	Why Japanese knotweed is a problem Find out why Japanese knotweed has become such an issue and the potential problems it can cause within your property. Why Japanese knotweed is a problem
	Japanese knotweed survey Unsure if you have a Japanese knotweed issue or you just simply want to determine the extent of your Japanese knotweed problem. More about a knotweed survey