Worm Keeping in the Winter

Take care of your compost worms during the winter with these tips.

| June 2018

  • Keep your worm farm in good shape over the winter.
    Photo by Getty Images/PhotographyFirm
  • “Compost Revolution” by Helmut Schimmel combines classic and cutting-edge research with real-world experience in gardens and horticultural applications.
    Cover courtesy Acres U.S.A.

Compost Revolution (Acres U.S.A., 2018) by Helmut Schimmel teaches alternatives to conventional composting, particularly those using earthworms. Worm composting is a superb alternative to traditional composting methods, which generally suffer from high-energy losses. Working in harmony with the below-surface army of microorganisms, the lowly earthworm is now known to be the true hero in the underground, a soil builder par excellence, not only in nature, but also in garden- and farm-scale composting systems. This section explains how to care for your worms during the winter. 

Important Steps to Take in Winter

I consider maintaining fermentative heating in the food substrate to be the most important factor for keeping worms through the winter. It has the greatest effect on seamlessly carrying on composting through the winter months. The importance of adding food is exemplified by its threefold function during the winter: it causes heating (together with the soil microorganisms), it delivers nutrients, and it protects life in the compost pile from outside influences. I have come to the following conclusions with regard to winter care.

Be prepared for the first frost. The wise man plans ahead. When the time is right, add food reserves such as a few sacks of chopped fall leaves that can be effectively employed as insulation if needed. Alternatively, it can serve as food if mixed with other types of waste.

The nature and size of your worm container have a non-negligible effect on their capability to survive the winter.



It’s important to enter the winter with well-heated compost material. If the compost starts out cooled down and waterlogged, it will be difficult to get it going again as the cold sets in. Most small-scale worm keepers end open-air vermicomposting at the first frost according to the motto: once everything is frozen, nothing is happening any more. Some complain that they no longer know what to do with their kitchen waste at this point. For me, this sort of waste becomes even more important in winter, as it is one of the few food sources that will continue to build up and is capable of generating a good amount of heat.

Making it through the first prolonged period of frost requires more food than usual. This makes it beneficial to be able to draw on additional food reserves. If a period of severe frost is imminent, maintaining proper heating is essential so that “the oven doesn’t go out.” The desired fermentative heating doesn’t appear immediately.

If the heating is insufficient when it does appear, there’s always the option of making use of exterior protective measures to limit the amount of heat loss. There are a number of different materials that can be useful for this purpose. For example, I use chopped leaves to insulate heat. I also make frequent use of cardboard, which can be laid directly on the food layer in large pieces. During heavy frosts, I use sheets of polystyrene foam. They are light and contain lots of air (making them good insulators). I weigh them down with rocks so that they stay pressed firmly in place. On the outside, I cover everything with a watertight tarp that is held up in the middle so that it doesn’t lie directly on the compost material, leaving it enough room to breathe. The compost’s air and oxygen supplies must be maintained in the winter as well.

Even the longest period of frost will eventually end and be replaced by thawing and mild temperatures. It is absolutely necessary to take life-sustaining measures during this time by adding the kitchen waste and used animal litter to the open worm container in order to provide the worms with desperately needed food replenishment.

The two measures, adding increased amounts of food and protection against cold from the outside, are usually enough to sufficiently protect the worms during the winter. The worst thing that can happen during the winter is lengthy, sustained periods of heavy frost. These can lead to occasional weather-caused disruptions but they don’t necessarily lead to significant losses of worms. The vermicomposting is just disrupted, and the mature worms migrate to the remaining pockets of warmth or enter a state of torpor. Young worms that cannot yet move well are at risk; they have limited reserves and are the first to fall victim to frost. To my knowledge, hibernation, where the worms wait out the winter at deep depths while coiled together alone or in groups, is only practiced by deep-burrowing worm species such as the well-known common earthworm (Lumbricus terrestris), not by Eisenia.

Observations On Cold and Frost Resistance      

I want to use an example to demonstrate the astonishing cold and frost resistance that brandlings from the genus Eugenia can demonstrate. After a two-week cold period at the end of 2005 with intermittent sustained frosts with temperatures reaching 17.6 degrees Fahrenheit and lower, it wasn’t just water drums that were frozen, but even one drum of mine that was half-filled with cow manure and water.

On the surface of the water-manure mixture, I discovered a number of brandlings that must have entered the drum when it was warmer. They were frozen and immobile (torpid). After the thaw, some of the worms were submerged in a puddle of water. The worms’ bodies looked pitiful and didn’t move when I tapped them with my finger. I wrote them off. The other worms that were not in the water also remained immobile, but I could detect signs of life in the form of faint motion when I tapped them with my finger.

I decided to take advantage of this incidental observation and carry out an experiment on the survival odds of the creatures I’d discovered.

More from Compost Revolution:

Vermicompost for Beginners

Excerpted with permission from Compost Revolution by Helmut Schimmel. Published by Acres U.S.A., © 2018.








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