COLUMN: Earthworms are your garden’s foot soldiers

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I was brushing up on my War of 1812 history the other day and was impressed to read that several hundred sailors marched from Halifax to Kingston during the first winter of the war. They were needed to man the new boats being built to fight the good fight on the Great Lakes. Imagine that: no decent roads, sleeping under the stars most nights, trudging through the snow most days by foot. They would have had neither the benefit of motorized transportation nor modern, waterproof footwear. 

This story reminds me of the many people that do yeoman’s service but seldom get thanks. Like the earthworms in your garden, who, for the purposes of this article, are people too.

I tell homeowners that it is a very good idea to rake fallen leaves off of your lawn and on to your garden. The leaves mat down with rain and weight of snow and begin to break down into a quality layer of organic matter. Come spring, when temperatures reach 10C, the earthworms move up to the surface of the soil and, upon discovering a fine harvest of leaves, munch on them until they disappear.

So, what happens to them? Glad you asked. This is December, the month to celebrate all of the good things in life and without a doubt, earthworms are one of them.


A gift to gardeners

Earthworms are part of a biotic community. They, along with centipedes, sow bugs and a variety of other useful earth-bound critters, provide an invaluable service. When earthworms arrive at the surface of the soil they consume the carbon and nitrogen-rich fallen leaves, and leaf mould. These are mineralized by microorganisms inside of the earthworm’s gut. As the leaves pass through the sophisticated digestive system of the worm they are converted into nitrogen-rich earthworm ‘castings’. As the worms move through the soil, sometimes as deep as a metre, they constantly leave these castings behind. They are a gift to the gardener.

The castings enhance the quality of your soil by stabilizing and storing nitrogen and carbon until the microbes in the soil break them down. As the worms move through your soil they open it up, essentially aerating it, making oxygen available to the roots of your plants.

With healthier roots your plants will perform better, the need to fertilize is minimized —or it disappears — and water moves through the soil more efficiently. Plants more easily channel their roots through the tunnels created by the earthworms.

It is worthwhile noting that there are no native earthworms in Canada. If they existed at one time, as fossils suggest they did, they were wiped out by the last Ice Age. Your friendly neighbourhood earthworms are immigrants. Either they moved up here from the deep south, where the glaciers never existed, or people brought them over here from Europe during the great plant importing schemes of the 1700s through to 1940. 

To nurture the worm population in your yard it is useful to know:

• Worms prefer loose, open soil. Turning your soil each spring helps to encourage them.

• They are moisture sensitive. During drought they move deep into the soil and enter a resting phase.  In heavy rain they move to the surface of the soil to escape the lack of air in their tunnels.

• Many chemicals are known to do permanent damage to earthworm populations, including carbaryl, malathion, and diazinon.

• One active worm will process up to one fifth of a kilogram of organic matter per year.

• An earthworm can live between three and 10 years depending on the species and soil conditions.

Earthworms are one of the unsung heroes of the garden. They are essential weapons in our war against poor quality soil. 


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Mark Cullen is Canada’s best-known gardening broadcaster and writer. He is the spokesperson for Home Hardware Lawn and Garden. Sign up for his free monthly newsletter at and watch him Wednesday mornings on Canada AM. His column, which focuses on our growing zone, appears in the Hants Journal every two weeks.



Organizations: Canada AM, Hants Journal

Geographic location: Halifax, Kingston, Great Lakes Canada Europe

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