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Worms, Worms, Worms

Judy Matthew, Class of 2010

My compost pile attracts many worms which come up from the ground and climb into the compost. The worms improve both the physical and chemical composition of the compost. The worm castings (worm waste) add beneficial bacteria to the compost which when spread around the garden, stimulates plant growth and can help protect plants against some diseases. The worm castings also help the compost-amended soil retain water. Earthworms play a major role in decomposition, while also serving as a valuable food source for birds and other earthworm-eating organisms.
As I work with my compost, I have taken many pictures of the worms and they are very red so I wondered if they are a native species or the famous “red wigglers” - which I never purchased.

My worm research revealed that regardless of whether the earthworms present in a given area are native or exotic, they influence soil fertility. By breaking up plant residues on the soil surface and mixing them with the topsoil, earthworms bring these materials into contact with the soil microorganisms that carry out decomposition and the formation of soil organic matter. The microorganisms themselves are a nutrient-rich food source for earthworms, and are ingested along with soil and plant residues. The worms return these nutrients to the soil, primarily in their feces, known as casts, which are readily available for uptake by plants. Earthworms also facilitate the transport of microorganisms throughout the soil, and have been shown to promote the colonization of plants by symbiotic fungi (mycorrhizal).

As I worked to get an understanding of worms and which variety I might be dealing with, I found an article that contained a treasure trove of information about worms. The Pacific Horticulture Society article, “Garden Allies: Earthworms” written by Frederique Lavoipierre, is a thorough primer on the topic of worms. I’ve excerpted some of the highlights below.

"An important agent of decomposition, earthworms are the ultimate recyclers. While most earthworms feed on plant material and ingest soil in the process, some thrive on an earthier diet.Earthworms can be divided into three groups:
  • Epigeic worms, which include the common red wiggler used in compost bins, live on the surface of the earth and eat rotting organic matter. They have a high rate of reproduction, useful to anyone starting a worm composting system.
  • Endogeic worms live within the soil, build lateral burrows, and are the only worms that eat large quantities of soil. They have little effect on surface litter, but prefer soils rich in organic matter, where they may play a role in decomposition of dead plant roots and in aeration.
  • Anecic worms, also known as nightcrawlers, come to the surface at night to drag leaves and other organic matter into their deep and permanent vertical burrows. Anecic worms play a central role in the decomposition of leaf litter, and soil formation, wherever they are found.

Some Worm Facts


About 180 species of earthworms in a dozen families in America, north of Mexico (Canada and USA); over thirty percent have been introduced. Worldwide, approximately 4,000 species of earthworms.

Life Cycle

Earthworms are hermaphrodites, with both male and female reproductive organs. One to several eggs are enclosed in a cocoon. Worms average six months to two years to reach adult size. Some earthworms are parthenogenic (able to reproduce asexually). Red wigglers may produce over 900 eggs in a year; nightcrawlers produce only about forty.


Immature earthworms look much like adults. Red wigglers are small (2 to 5 inches), reddish-brown and striped; red marsh worms are larger (2.5 to 6 inches) and more purplish; nightcrawlers (4 to 12 inches) are pink to dark red.

Life Span

Varies from about a year for red wigglers to six years for nightcrawlers.


An earthworm can eat its own weight in organic matter daily. Red wigglers eat decomposing materials at the surface; red marsh worms eat decomposing roots and soil in the top foot, while nightcrawlers live up to six feet underground, coming to the surface for organic material. Some worms thrive in acidic conditions, such as decaying conifers; some in the mud of streams.

Interesting facts

  • Oregon and Washington are home to giant (but elusive) earthworms, said to smell strongly of lilies.
  • More than a million earthworms may be found in an acre of land.
  • A single earthworm may produce up to ten pounds of castings per year "

Have a look around your garden, what worms do you see? As for me, I have learned a lot about earthworms…but I am still wondering if my terrific compost worms are red wigglers or a native Californian species…

Learn More

You can read more about worms in the following recommended articles and a fun video:

  • Garden Allies: Earthworms, Pacific Horticultural Society, Frederique Lavoipierre: https://www.pacifichorticulture.org/articles/earthworms/
  • All About Worms, Penny Pawl, UC Master Gardener of Napa County: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=27117
  • Check out this practical tip sheet about keeping worms from the Master Gardeners of Sonoma County: "Putting Worms to Work and Keeping them Happy” 
  • If you have little ones (or are young and heart) who are learning about the garden, have a quick look at this reading of the fabulous book “Diary of Worm” written by Doreen Cronin and pictures by Harry Bliss