Japanese Knotweed Identification
It's relatively easy to identify Japanese knotweed if it hasn't been concealed. If you've spotted a suspect plant take a look at our Identification Video above, this shows what Japanese knotweed looks like during the different seasons, and some plants that commonly get mistaken for Japanese knotweed. We've also produced a Japanese Knotweed Identification Guide, which you can download to help you identify the plant on site. You can also look at our Japanese Knotweed pictures to show further examples of the weed in different seasons.
If you are still unsure, we offer a Japanese Knotweed Identification Service. Email us photos and we'll tell you if Japanese knotweed is present. We don't charge for this service but if you would like to make a small donation to a worthy charity that would be appreciated.
How can I identify Japanese Knotweed myself?
Japanese Knotweed remains dormant over the winter months. Don’t be deceived by its lack of growth because the rhizome remains and can grow underground.
In spring time and sometimes as early as March, you will be able to see red or purple shoots appear from the ground. These shoots will rapidly begin to grow into long canes which over time will turn green in colour. Knotweed is fully grown in the Summer months and develops a distinctive speckled pattern. You will notice that mature stems are hollow and have small purple spots. The weed can grow up to 3-4 metres high and grows extremely quickly.
Japanese knotweed is fully grown by early summer and mature canes are hollow and can stand up to 3 metres high. The plant flowers in late summer and these consist of clusters of spiky stems covered in tiny creamy-white flowers. The leaves are luscious green in colour and usually flat and often shovel or heart shaped in appearance.
In late autumn the leaves will fall to the ground and the cane becomes dark brown in colour. Whilst the cane will often remain standing throughout the Winter months, the plant will continue to grow underground. The roots will be orange or yellow, with established roots appearing larger whilst younger nodes, known as knots, being smaller in size.