Hot weather actions

Compost worms can adjust to a wide temperature range. However, at bed temperatures much over 30oC worms become stressed and can die if temperature remains high for sustained periods. Here are some handy tips to keep your worm farm safe over the hot months;

  • Make sure your bin is located in the coolest place you can find, and never place it in direct sun during the warmer months.
  • Remember it is the temperature of the bedding not the air temperature that is critical, and bedding is slower than air to heat up. There is generally no issue on hot days if the temperature drops significantly at night.
  • Keep a thermometer handy, preferably one with a probe that can reach the centre of the bin (which will be the coolest part of the bin). If the temperature in the castings start to head toward 30oC it is time to take action.
  • If the bins start to heat up over 30oC bury plastic bottles of frozen water (2 litres +) into the top of the castings. Remove bottles as soon as they melt and replace with fresh frozen bottles if bedding is still warm.
  • Avoid adding more water when the bins are hot as excessive moisture can make it more difficult for the heat to escape. Also avoid adding ice cubes on their own as once the ice melts the excess moisture can heat up quickly – if you are using ice keep it contained in a bag or plastic container and remove once it melts.
  • Feed the worm farms cautiously during hot weather. There should never be more than a couple of inches of uneaten food in the bins at any time. Excess food can heat up and create toxic conditions which will further stress the worms.
  • Watch your worms for stress behaviours like trying to escape the bin . – poorly functioning bins can suffer heat stress at lower temperatures and healthy bins have been observed to still function safely over 32oC.
  • Cover the bin with a hessian sack or wet blanket – monitor it and keep spraying water onto the as it dries out. This creates a cooler microclimate around the worm farm.
  • If you are going away for an extended period, consider removing the top active layer of your worm farm (with the majority of worms in it) into a large tub or other container and keeping it indoors in a cool place. The worms should be safe for a couple of weeks – make sure the place you put them will stay cool during different times of the day or you may come home to an unpleasant surprise!
  • Finally, don’t be too discouraged if you lose your worms – of course this is something we want to avoid, enough worms will generally survive for the worm farm to recover, and there are usually worm eggs throughout the castings which will hatch once conditions improve.