Earthworms in Gardening: How to Attract and Use Earthworms

Earthworms are invertebrates, or animals without backbones, that belong to a subclass of annelids, or segmented worms, called Oligochaeta. The common earthworm is a member of the species Lumbricus terrestris. There are more than 200 species worldwide, including green worms, giant earthworms, and several species native to Europe and Africa. In North America, they are known by many names, including nightcrawlers and angleworms (for their frequent use as fishing bait). In other parts of the world, they are known as dew worms or lobworms.

Earthworms are externally segmented, with setae, or bristles. Each of their segments helps them navigate through the soil. They breathe through their skin and have a dual circulatory system that carries nutrients, removes waste, and stores reproductive material.

These invertebrates are hermaphrodites, which means they have male and female reproductive organs. Earthworms mate at night and fertilize the clitellum—a thick band around their midsection—then form a cocoon that incubates the larvae until they hatch after approximately three weeks.

All earthworms eat humus or decaying organic matter like leaf litter and plant matter. They also eat fungi, nematodes, bacteria, and other microorganisms and decomposing animal matter and waste.

There are three types of earthworms, categorized according to their habitats:

1. 1. Epigeic earthworms, or compost earthworms, do not burrow in the ground but instead live on the soil surface.
2. 2. Endogeic earthworms live in semi-permanent horizontal burrows in the topsoil or the first five to ten inches of soil.
3. 3. Anecic earthworms live in deep, permanent vertical burrows under the ground and subside on organic material from the surface. Anecic earthworm burrows can grow up to six feet in length.

Earthworms affect the soil in a variety of ways. They include:

• Aeration: Earthworms improve garden soil structure and loosen soil compaction through soil aeration. When earthworms burrow, they churn up the soil, providing plant roots with more oxygen and growing deeper into the ground.
• Aggregation: Worms consume organic material and excrete them as castings (poop). Worm castings are rich in nutrients like calcium, phosphorus, and magnesium, as well as microbes from the microorganisms they consume as a food source. Soil aggregation binds together these elements, which are essential for plant growth and soil health.
• Infiltration and water-holding: Earthworm activity also improves porosity, which allows the soil to hold more water and drain more efficiently. Burrowing also reduces water erosion on the soil surface.
• Residue: Earthworm casts bury plant and crop residue when gardeners deposit them on the soil surface. They also pull that residue into the soil when they burrow, which helps grow healthy plants.

Earthworms may be beneficial to potted plants in certain ways. These include:

• Pest control: Earthworms consume invasive species like plant-parasitic nematodes, or roundworms, which devour plant roots. Worm castings also contain an enzyme that repels aphids, whiteflies, and other plant bugs.
• Soil health: Earthworms aerate the soil in indoor plants, just as they do in a garden bed. Earthworm casts also enrich the soil in houseplants with nutrients. Eisenia fetida, or red wigglers, are among the best types of worms for potted plants. However, it’s important to use organic potting soil or add organic composting material like kitchen scraps or coffee grounds to the soil. Most potting mixes contain peat or coco fiber, which decompose slowly and lack the minerals worms need.
• Fertilization: Worms can be an effective organic fertilizer for potting soil. Vermicomposting—using worms to decompose organic matter and food scraps—is a great nontoxic alternative to chemical fertilizer. Create a worm compost bin by filling a deep container with a layer of shredded newspaper or corrugated cardboard for burrowing. Add organic soil or compost material to the worm bin, and then introduce composting worms like nightcrawlers or red wigglers. Mix the worm casting with the potting soil to fertilize it. Learn about using worm tea as fertilizer.

There are many ways to attract earthworms to your garden:

• Avoid pesticides: To encourage earthworms to help the soil in your vegetable garden, avoid using pesticides. While earthworms can self-detoxify when exposed to certain chemicals, it takes a toll on their systems.
• Mulch your garden: Organic mulch will attract many worms to a garden. Add organic material like lawn clippings and dead leaves to the soil surface, till it into the soil, and add a top layer of mulch. Lightly water and aerate the area, then dig a foot into the soil to see how many earthworms you have attracted. Watch for jumping worms, which resemble earthworms, but produce casts that leave garden soil grainy and dry.
• Transplant worm-filled soil: Add a few shovelfuls of soil filled with worms to areas in your garden that do not have them. You can grow your worm population by adding worm eggs or cocoons to the soil.

Grow your own garden with Ron Finley, the self-described "Gangster Gardener." Get the MasterClass Annual Membership and learn how to cultivate fresh herbs and vegetables, keep your house plants alive, and use compost to make your community—and the world—a better place.