What does Japanese knotweed look like?

Why pictures are essential for compensation! 

It has been said that, 'a picture is worth a thousand words', and indeed this could not be more true for claimants of Japanese Knotweed infestations.  Our Southampton-based client sent us her photos and asked the essential question: what does Japanese knotweed look like? 

The images below show a large infestation of Japanese knotweed in a neighbours garden. Providing photographic evidence of infestations is essential for those making an insurance claim. 

japanese knotweed in garden
Japanese knotweed growing in neighbours garden
japanese knotweed growing over neighbours fence

What is the structure and features of Japanese knotweed? 


Japanese knotweed is a plant consisting of a rhizome, or root, hollow stems, and thorn-shaped nodes - in fact, it looks a little like bamboo.  Like an iceberg, the majority of the plant lies underground - up to 3m deep.  However, it can also grow to 3 meters tall, and rapidly spreads far and wide. In full bloom, the leaves can span over 20cm in length. 

Japanese knotweed rhizome (root)

So what does Japanese knotweed look like throughout the year? 

Like many plants, Japanese knotweed changes in appearance season by season.  Here's how the identify this invasive weed during its growing cycle:

young Japanese knotweed shoots, looks like asparagus


  • New shoots will emerge in March and April 
  • They look like asparagus and may have a red/purple tone
  • Green leaves and stems will unfurl from the crown and establish themselves on the ground.


  • As it gets warmer, Japanese Knotweed will spread quickly, searching for light and water.
  • The stems are like bamboo, with visible joints and knots. They are hollow and speckled with red or purple.
  • Leaves are lush green, shaped like a heart or shield and can grow up to 22cm in length. 
  • During this time the plant can grow over 3m tall. 

close up of Japanese knotweed leaves
Japanese knotweed in flower


  • In late summer, Japanese Knotweed develops clusters of spiky stems.
  • Tiny white flowers appear at the end of the zig-zag like canes. 


  • Approaching winter, the leaves will fall and the canes will brown.
  • After the first bout of frost, the stems may appear to be dead - they are not - unfortunately, the rhizome can remain dormant below ground for many years. 
So with its changing nature, and its ability to spread, photographic evidence is essential for those making an insurance claim relating to an infestation.
Japanese knotweed dying back in winter

Photo Diary and Documentation for Legal Purposes

During a six-week podcast show with Affinity Finance, barrister Tom Carter expressed how essential photographic documentation is to a Japanese Knotweed claim. He says: "It is difficult to prove date of actual knowledge, which is why a photo diary or record is helpful". 

During a legal dispute, it is necessary to disclose the actual date when you first became aware that Japanese knotweed was growing on your property.  For defendants, it is especially important to provide evidence showing past and present efforts to eradicate the infestation.

It is advisable to keep a daily photo diary of the plants growth, though we understand this may not always be possible.  However, at the very least, a bi-weekly photo diary is suggested.  

Examples of Photographic Evidence

We suggest photographing the following: 

  • The extent of the Japanese knotweed;
  • The plants leaves, stems and buds for official identification;
  • Showing knotweed in the context of your property boundary - for example, if Japanese knotweed has spread from your neighbours garden to your own, a picture taken from a first storey window may show a fence boundary;
  • Where Japanese knotweed has likely spread from a neighbouring property or land;
  • Any damage that has been caused, or is being caused.

Showing the untreated spread of Japanese knotweed over time will help property owners when it comes times to make a claim.

Next Steps

For assistance in identifying Japanese knotweed, send us your photos.  Remember, keep a photo diary and it will help support your claim.  Dr. Knotweed and co. are here to help.  We will get to the root of your Japanese knotweed problem. To avoid further damage, contact us for a quote today.  

Date: September 30, 2020