After the latest hotspots for Japanese knotweed in Suffolk have been revealed, here are some ways to spot it. 

Japanese knotweed is a non-native, invasive plant that was imported to the UK in Victorian times and is known as a pest species that outcompetes native plants and causes damage in the built environment. 

Where are the latest hotspots for Japanese knotweed in Suffolk? 

Experts have said that this invasive species is currently thriving ahead of its usual growing period due to warmer and wetter weather this winter. 

The latest hotspots for Japanese knotweed in Suffolk are Ipswich, Lowestoft, Stowmarket, Sudbury and Bury St Edmunds. 

How do you identify Japanese knotweed? 

The appearance of Japanese knotweed changes with the seasons and is harder to spot in autumn and winter so it is important to know how to spot it. 

Key traits of Japanese knotweed: 

  • Red shoots emerge in Spring that look like asparagus. 
  • Leaves that are shield or shovel shaped. 
  • Stems that resemble bamboo canes with purple speckles. 
  • Small, cream-coloured flowers developing towards the end of summer 

What does the start of Japanese knotweed look like? 

As mature Japanese knotweed begin their growth thick, upright stems pierce the ground and can grow 10cm in height per day until they reach their full height at the end of spring. 

Following this rapid growth, these stems or canes resemble bamboo and will usually reach 1m or more in height before any leaves or side branches begin to grow. 

The start of Japanese knotweed where it is newly imported, disturbed or spreading out naturally can look completely different. 

New shoots tend to be smaller, deep red or dark green with deep red leaf edges and open into leaf much earlier. 

It can also look different when it starts to regrow from a failed herbicide treatment, which is known as bonsai growth. 

What will happen to Japanese knotweed in the run up to Winter? 

Over the next few weeks knotweed will start to die back, as temperatures cool and light levels drop sending the plant into its dormant winter phase. 

Its green leaves will die and fall from the branches, the stems will turn brown and brittle, and after the first few frosts the plant will have completely died back leaving only the dead canes remaining. 

The plant will re emerge next Spring so autumn and winter is the ideal time to evacuate it when the garden is not in use. 

How do you identify Japanese knotweed in Winter? 

Things to look out for are: 

  • Brown brittle canes left standing. 
  • Distinctive crowns in the ground. 
  • Scorched areas of grass and bare patches of earth. 
  • Smaller plants with distinctive zig-zag stem distribution. 

How many houses are affected? 

Environet estimates that approximately 5% of homes are currently affected by Japanese knotweed, either directly or by neighbouring an affected property, typically impacting property prices by around 5% - or up to 10% in severe cases. 

There are a total of 264 verified knotweed sightings in Suffolk, or 0.07 incidences in every 1km².