Japanese Knotweed is an invasive plant that can cause chaos in homes and gardens if left untreated.

It has been described as a "horticultural horror story" by some experts, due to its menacing growth rate and its deep roots. It can also shatter concrete and patios.

While it is not illegal to have Japanese Knotweed growing on your property, it is illegal to allow it to spread into the wild.

Homeowners are rightfully concerned over the spread of Japanese Knotweed in their area. According to Environet, experts in removing invasive plants, these are the Cambridgeshire hotspots for Japanese Knotweed:

  • Huntingdon, St Ives and St Neots all have cases of Japanese Knotweed
  • In Ely there are seven cases of Japanese Knotweed per 4km
  • Chatteris and March have been flagged as hotspots
  • Peterborough has 24 cases of Japanese Knotweed per 4km
  • Cambridge has 35 occurrences per 4km

Click here to access the Environet map which shows the hotspots.

How to get rid of Japanese Knotweed

If you decide to tackle Japanese Knotweed yourself, the expert suggests herbicide treatment as an option.

Here's a breakdown of the steps involved:

Plan Meticulously: Before diving in, assess the surrounding area. Are there nearby schools, playgrounds, or water sources that could be affected by herbicide overspray? Inform your neighbours about the treatment schedule to minimize exposure risks. Choose a late spring or early autumn window when the plant is actively growing.

Safety First: Don't underestimate the importance of proper safety gear. Wear overalls, a safety mask, gloves, and a face shield for protection. Sheets, tarpaulins, and rubble sacks will also come in handy.

Weather Matters: Choose a dry day with no rain forecast, as most herbicides can harm desired plants as well. Avoid windy conditions if using a spray application.

Targeted Application: A garden sprayer is effective for applying herbicide, but use caution near water sources or sensitive areas. Alternatively, a roller, cloth, sponge, or brush can be used for localized application. Remember to wear gloves and shield nearby plants with tarpaulins. The herbicide should thoroughly cover the leaves and stems. 

Careful Disposal: Once cut, place all Knotweed material in sturdy plastic rubble sacks. Remember, this is hazardous waste and requires disposal at a designated landfill site. Check with your local council to see if they offer any collection services for Japanese Knotweed.

Persistence is Key: Eradicating Japanese Knotweed is a long-term battle, not a quick fix. A single treatment won't do the trick. Be prepared to repeat the process 2-3 times a year for several years (3-5) until the weed is completely eradicated and shows no signs of regrowth.