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Credit: Sheena Adams

A sure sign of healthy soil is an abundance of worms.

An earthworm’s job is to condition the soil by aerating it and digesting organic matter. Soil with many worms will be loose, porous and full of nutritious worm castings containing nitrogen, phosphorus, potash and magnesium. On average, an earthworm produces its weight in castings every 24 hours. The tunnels made by earthworms allow water and air to enter the soil and make it easier for plant roots to penetrate. There are more than 1,000 species of earthworms in our soils and compost boxes. Quite often I am asked about the differences between worms in the compost pile and those in garden soil, and whether it’s all right to put worms from the garden into the compost bin to get it going.

Yes, there are differences, and, no, you should not add garden worms to the compost or red wrigglers to the garden. The large, bluish-pink worms you see after a rainfall are true soil dwellers. They prefer to live deep in the soil, where it is cool and damp. During dry summer months they often take shelter several feet below ground level. Since they prefer cool temperatures, they will not perform in a hot compost or manure pile. You may find, however, that in a deep compost pile they will migrate to the bottom layer where it is cooler and the organic matter has been broken down. These worms, sometimes referred to as night crawlers, are prime aerators in our gardens, digesting the organic matter in the soil and turning it into humus.

In compost, fallen leaves or manure piles, you will find small red wriggler-type worms. These surface-dwelling worms are generally 5 cm (2 in) long and are ferocious digesters of organic matter. Once the organic matter in one area is decomposed to humus, they move along. Red wrigglers prefer warmer soil temperatures and plenty of fresh organic matter; therefore will not perform deep in the soil. Red wrigglers can be purchased at garden centres and added to any new or existing compost. Earthworms have earned their reputation as garden tillers, and red wrigglers are great recyclers, so welcome them into your garden and get them working for you.