Worm Bin Temperature
Red wiggler worms thrive in temperatures between 55° and 75° Fahrenheit (12° to 24° Celsius). They will slow down reproduction and feeding in extreme heat or cold, and can even die if the temperatures get too extreme.
Use a thermometer to check the temperature of the bedding in your worm bin.
When monitoring the temperature of your bin, it is important to remember to measure inside the worm composter, because the temperature of the moist bedding is usually lower than the outside air temperature. You can use a soil thermometer to measure the temperature of your worm bin bedding.
If your worm bin conditions are too cold, worms may congregate together in a ball that looks like ground hamburger meat to keep each other warm. If temperatures drop below 40° Fahrenheit (4° Celsius) for extended periods of time, your worms will die. There are several things you can do to keep your vermicomposter warm:
- Feed foods that are high in nitrogen; they generate heat as they break down. These include leafy greens, lentils, peas, tofu, broccoli/cauliflower, beans, oatmeal, and mushrooms.
- Insulate the composter – if it is placed on a cold surface, place a sheet of cardboard underneath it to help deflect the cold. You can also wrap the composter with cardboard or other insulating material to protect it from cold and drafts. Just make sure that it is not wrapped so tightly that airflow is restricted.
- Provide a heat source – a heat lamp or spotlight can be placed over the composter to help warm it and encourage worms to migrate up to the food. Make sure the lid is on because worms are sensitive to light.
If conditions in your worm composter become too hot, worms will begin to migrate into lower trays where it is cooler. This mimics their response to a hot surface temperature in nature as well. In temperatures that exceed 85° Fahrenheit (30° Celsius), your worms can die. Never place your vermicomposter in direct sunlight. There are several things to do to keep your vermicomposter cool:
- If your composter is outside in hot weather, find a shady spot with plenty of air circulation.
- Make sure you keep your composter moist in warm conditions.
- To increase airflow through the compost to cool it, you can place pieces of wood no more than ¼” thick between trays, separating them. This works best at night, and if you find that you need more air movement, you can add a fan. Just be careful that conditions don’t dry out.
- You can use ice in emergencies – place ice cubes in the upper tray and cover with a layer of newspaper. The ice will melt and filter down through the lower trays, cooling them. Only do this in an emergency and be careful of your compost getting too moist.