The Effects of Temperature on Earthworms

Common Types of Earthworms

• The common types of earthworm raised commercially include night crawlers, field worms, red wrigglers and red worms. Night crawlers (Lumbricus terrestris) are good for soil aeration and for fishing, but they are harder to breed than some other species. Field worms (Allolobophora caliginosa) are good for fertilizing gardens with their castings (waste) but can also be hard to raise commercially. Red wrigglers (Lumbricus rubellus) are efficient composters and prolific breeders. Red worms (Eisenia foetida) are also good composters.

Needs of Earthworms

• Although there are many species of earthworms, the differences in their biology are relatively minor, so their physical needs tend to be similar. Earthworms are saprophagous animals that digest decomposing organic waste. They require moisture to survive and thrive, and their bedding material should be crumbly and moist but not wet. Earthworms will grow over a wide range of pH (4.2 to 8.0), but they reproduce best at 7.0. They tend to avoid light, as it dries them out quickly.

Maximum and Minimum Temperatures

• Earthworms cannot tolerate freezing temperatures. Most commercial species do not thrive in temperatures below 45 degrees Fahrenheit, although red worms can tolerate slightly lower temperatures. The maximum temperatures for most common species are in the range of 85 to 90 degrees F. Temperatures lower than the minimum or higher than the maximum will kill most earthworms. In the wild, or in the garden, when earthworms are exposed to temperatures that are too warm or too cold, they migrate deeper into the soil to find a more suitable temperature range.

Optimal Temperatures

• The ideal temperature for earthworms depends upon what activity is desired. For optimal reproductive rates, the temperature for most species should be between 60 and 70 degrees F. For optimal growth and composting activity, a slightly higher temperature is desirable. Generally speaking, an increase in temperature increases their metabolic rate, which means they must consume more food (and do more composting), while lower temperatures mean they consume less.