Get us in your inbox


This is why London's canals have turned bright green

Written by
Rosie Percy

Earlier this week we posted a photo on Instagram that showed a stretch of the Hertford Union Canal in Hackney Wick looking greener than a Rio Olympic swimming pool. [Photo: Niall Horgan]

The radioactive-looking water caused quite a reaction, with many of you concerned about the safety of the canal. Let us clear things up: the Kermit-coloured water is caused by plants, not pollution. 

The Canal River Trust has confirmed that the green substance covering the canal isn't a new carpet, it's a whole load of duckweed. Each piece of the plant is only the size of a ladybird but multiplies rapidly in the heat – so sunburn in September isn't the only side effect of London's late-summer heatwave.

© @niallhorgan

The duckweed itself isn't harmful but as it gets thicker it can starve other wildlife in the canals of oxygen and trap litter which causes problems for boats, so the Canal River Trust is working to remove it as quickly as they can. In one week this year, they removed 70 tonnes of the green stuff.

The Trust is asking Londoners to make it easier to keep canals clear by avoiding throwing litter on the duckweed. They've also warned dog walkers to keep a close eye on their mutt as they can mistake the canal for grass, making for a very soggy doggy. 

Fancy a duckweed smoothie? There's talk it could be the next superfood

Popular on Time Out

    Latest news


      The best things in life are free.

      Get our free newsletter – it’s great.

      Loading animation
      Déjà vu! We already have this email. Try another?

      🙌 Awesome, you're subscribed!

      Thanks for subscribing! Look out for your first newsletter in your inbox soon!