Will Composting Worms Overwinter?
by Paulette Mouchet
Originally published in "The Rose Garden" newsletter, February 2004.
I was using my homemade vermicompost for planting my bare-root roses and got to thinking about how well the worms would survive in my garden since it's been so cold. I don't screen my vermicompost before using it so the compost contains lots of worms. I contacted Kelly Slocum, a vermicomposting consultant and overall Worm Wonder Woman. This is what I learned.
Most adult vermicomposting worms will not over-winter in the garden if temperatures drop below freezing for an extended period. Vermicomposting worms are epigeic or surface dwellers-they can't burrow to escape cold extremes so adults are killed by freezing temperatures. However, worm eggs, a.k.a. cocoons, are amazingly hardy. They can easily survive even Alaskan cold to hatch a new generation of baby worms when spring arrives.
Eisenai fetida, commonly called the redworm or red wiggler, is the species most commonly used in vermicomposting because it is most tolerant of environmental fluctuation, handling, and variation in feedstock. E. fetida is a prolific breeder and is found on nearly every land mass of the planet, thus there is little concern about introducing an alien worm species that might cause local environmental concerns.
If you want to increase the worms in your garden, the best way is to amend your soil with lots of organic material so localized worm populations will be drawn to all the yummies-sort of the "If you build it, they will come" idea. Remember, the type and number of worms currently living in your soil are the type and number that can be supported by your soil in its current state.
Worm populations will naturally achieve a status quo based on available food, space, and environmental conditions. Adding store-bought or vermicomposting worms is often a death sentence for them because the environment is not able to support them. If the environment was suitable for more worms, more worms would be present. If you want more worms in your garden, you must increase the food resources, and that means increasing soil organic matter.
Interestingly, worms don't actually eat the organic matter. They eat the beneficial bacteria and fungi that are on the organic matter.
Good worm foods to use in your garden include:
- oat hay
- alfalfa hay and meal
- composted redwood
- compost (be sure it's tested and certified)
- fish meal
- cottonseed meal
- shredded newspaper and cardboard (yup, they make a good mulch, especially under a layer of alfalfa hay)