Squiggling into Summer with Worm Composting

Our temperate San Diego weather is usually perfect for accommodating the red wrigglers used for vermicomposting. Their preference is for temperature ranges of 55 – 77° F, but they can tolerate temperatures above and below this range. Temperatures should be measured inside the bin since they can vary significantly from external measurements.

As we approach summer and fall when temperatures rise, you may need to make some changes to keep your worms alive. Once temperatures creep up toward 90° F, red wrigglers reach their upper threshold of heat tolerance and can start to die off if additional measures are not taken. Here are some techniques to keep them healthy:

  • If possible, move your bins to a cooler location. Find a deeply shaded place in your yard; the difference between sun and shade can be 10 – 15 degrees! Moving your worm bin to the garage, the basement, or a shed may provide a cooler environment. If you get really hot temperatures in your area, you may consider moving your bin inside.
  • Can’t move your bin? Find ways to keep the effects of heat via solar radiation minimized. Dark bins absorb heat. Paint your bin a lighter color or cover it loosely with a space blanket, which will to reflect light and heat. Remove the lid and drape with a moistened, light-colored sheet or burlap, which will draw cooler air into the bin. Make sure the ventilation holes in the bins are not clogged or obstructed.
  • Make sure bins are filled with bedding in order to provide insulation. Larger bins are less susceptible to temperature fluctuations. If your bin has multiple layers, make sure your working layers have damp newspaper. Place an empty tray under the working tray and fill it with damp crumpled or shredded newspaper. You can do the same in the bottom leachate capture layer in residential commercial bins. Leave the spigot open for increased airflow.
  • Hot weather increases drying – check moisture levels during hotter months. The bedding should be moist, but not so wet that you encourage mold or drown your worms.
  • Worms eat more in warmer weather, so you can feed them more often during the summer. You can freeze your food scrap before feeding it to your worms. This also facilitates food breakdown and helps kill off fruit fly larvae.
  • Consider in-ground bins.  Dig a deep hole in a shady location and lower your bin down into it – be sure to leave some space around the outside for airflow. Solana Center also sells worm bins made for burying in the ground. Give us a call or stop by to find out more.

Contact our “rotline” at (760) 436-7986 ex. 700, or via email at compost@solanacenter.org, with any composting questions.