As you may know, as the surrounding temperature drops, so will worm body temperature. When this happens, their body processes will start processing at a slower rate, which makes they more ‘sluggish’. The worms will move about slower, eat slower and create worm cast slower.
When the temperatures reaches down to near freezing point things can get so slow that it seems the worms do not move at all. This is when they hibernate to conserve energy and to stay alive.
As a Subpod owner, you don’t want your beds to reach freezing point. If you use your beds to recycle organic waste you don’t want the temperatures to be dipping so much that they can’t process food either. Fortunately there are some tricks to keep your worm beds insulated and warm. Please remember that the composting rate WILL be slower.
It turns out you have a variety of options of increasing sophistication:
1. Move the worms out of the Subpod into some buckets to a warmer location indoors in those very cold months
2. Add a cold frame on top of your Subpod
3. Build or purchase a small below ground greenhouse
For more details on these options, see below:
If you move your Subpod into a basement in the winter months that is not as cold, the worms can keep composting for you through the cold months.
Insulation is a great economical way to keep your worm bed warm.
These materials are fluffy by nature and contain millions of small pockets of air which helps trap heat in. By simply digging and burying your Subpod in the ground or snow, the Subpod can be protected from the harsher temperatures outside.
Instead of burying it, you can also surround your bin with some insulation material such as polystyrene (if you have some waste lying about), thick carpet or even a clear plastic covering (which not only traps heat, but creates a greenhouse effect).
Within the Subpod, the upper surface can be protected by adding a thick layer of straw, hay, grass or even dry leaves. These materials are great as it again creates pocketfuls of air. With straw and grass, they may even generate a small amount of heat in the right conditions.
Some people have gone further and purchased electric heaters to help raise temperatures of their worm bins.
These can be easily bought from aquarium shops where the heaters are used to heat ponds and aquariums. These are mostly a metal rod which heat up and are relatively inexpensive. They can keep certain areas of your Subpod warm.
Metal Heating rods usually range in temperatures of 23 – 35°C. But it may be easier to just turn them up to its maximum and stick the rod through the center of the Subpod. This will prevent the center and the surrounding areas from freezing. The risk is the castings around the rod may dry as it warms, so you’ll need to check from time to time.
The worms will also adjust their own position to find the spot most comfortable for them. If the area is too hot, the worms will move further away from the rod. The most important thing is not to let the area freeze. With the center being the warmest point and being the place less likely to freeze, the worms will start to gather around that area.
It will be best to feed around the area of the heat rods since this is where the Subpod will be most active. If done correctly, you may even be able to keep the rates up as they were in autumn!
If you create a cold frame above your worms, you can retain warmth and the worms will keep composting, in some climates.
If you live in a really cold place, it might be worth making a small below ground greenhouse to grow year round and keep your worms happy. There are some interesting ideas out there. For example: https://www.gardeningknowhow.com/special/greenhouses/what-are-pit-greenhouses.htm
Worms may die when they freeze, but the eggs will survive in cocoons and emerge into new worms in Spring.
Please contact your local worm supplier and ask which are the best compost worms in your area to survive the cold winters. They may even have some tips and tricks for keeping your worms warm during the colder months.
A lot more information is available online if you do a search - they go into all the winter preparation techniques.