Worm farming in winter

Worms thrive when the outside temperature is between about 55 and 80 degrees F. (12 to 26 C.). When the air begins to turn colder, the worms get sluggish, refuse to eat, and sometimes even try to escape their environment to search for a warmer climate.

What happens if you just leave the worms outside? Worm activity slows down as the temperature drops. Below 40 degrees F. (4.4 C), the worms will be at risk of succumbing to the cold. They will burrow toward the warmest part of the bin: the bottom and center.

Any organic scraps that you add will increase the temperature slightly. The process of decomposition generates some heat. However, this may not be enough to keep the worms alive.

When the conditions are right, adult composting worms lay eggs. Worms are simultaneous hermaphrodites. This means each worm has female and male reproductive organs. Contented composting worms exchange DNA and produce cocoons. These cocoons survive freezing temperatures. With a little luck, new worms will hatch in the spring. Therefore, leaving the worm bin outside in the winter probably won’t be the end of your composting program.

Cold climate vermiculture, or worm farming in cold weather, consists of fooling the worms into thinking it’s still autumn and not yet winter.

The easiest way to do this is to remove the worms and store them somewhere fairly warm, such as an insulated garage or cool basement, or even bringing them indoors.

Barring that possibility, you’ll have to create an insulated environment to keep your worms alive through the winter.

Actions you could take

  • The first step in vermicomposting when it’s cold is to stop feeding the worms.
    • When the temperature lowers, they stop eating and any food leftovers may rot, encouraging organisms that can cause disease. The idea is simply to allow them to live through the winter, not have them create more compost.
  • Insulate the compost heap with 2 to 3 feet of leaves or hay, then cover the pile with a waterproof tarp. This will keep in the warmer air and keep out snow, ice, and rain.
  • Try burying leftover cooked rice in the compost before covering it. The rice will break down, creating heat during the chemical process.

As soon as the weather warms to above 55 degrees F. (12 C.), uncover the pile and feed the worms to help them recover.

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