Are Worms Good for Plants?

Earthworms are often a sign that your soil is healthy.

Earthworm in damp soil.

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The most common worms in gardens include earthworms (often called nightcrawlers), nematodes, and the worm-like larvae of beetles, moths, and caterpillars. Generally speaking, earthworms are beneficial, nematodes can be either beneficial or harmful, while insect larvae are more likely to be harmful.

Here's why and how you should cultivate earthworms in your garden.

Benefits of Earthworms

What's good for earthworms is good for plants. Similarly, an absence of worms in your garden might indicate that your plants won't thrive there either. Along with microbes, earthworms help complete a cycle of life underground that's vital for healthy plants.


Earthworms break down dead plant matter, making the nutrients available to new plants. Earthworms tunnel through the soil, distributing those nutrients rather than leaving them where the organic matter was broken down.

Earthworm castings also make great fertilizer for your plants, adding nitrogen, phosphorus, potassium, and magnesium—four of the most important elements in a plant's diet.


The organic matter that worms break down is also food for beneficial microbes in the soil, which further the process of making it available to plants. And as anyone who has watched a robin feed knows, earthworms are an important element in the diet of many birds. Those birds in turn are beneficial to plants by reducing the number of pests. A complex, diverse environment helps grow strong plants.

Soil Structure

Earthworms build small burrows, which creates underground air pockets. (Earthworms breathe oxygen through their skin.) Plants need oxygen, too. The pockets also help the soil retain water, which, in turn, can keep the soil cool in a hot area. Loosening the soil makes it easier for plants to push roots through, rather than a more heavily compacted soil.

How to Cultivate Earthworms in Your Garden

Unless you're starting with brand-new soil, it's likely that there are already worms in your garden. A sustainable method of cultivating worms is just to let them naturally populate your soil rather than purchasing commercially grown worms. Fortunately, cultivating a healthy environment for worms also creates a healthy environment for plants.

Provide Worm Food

Earthworms alone won't do much good to your plants if there is no food present to sustain them. Add organic matter such as leaf litter, grass clippings, or a compost mix. Commercial compost is great for plants but not for worms, since the compost has already been digested in a commercial facility.

When your annual flowers and vegetables have finished for the season, snip off the above-ground plant and leave the roots in the soil as worm food. Also, make sure to avoid pesticides, fungicides, or fertilizers, which are all too easily absorbed through worms' porous skin.

Maintain Welcoming Soil

Earthworms in soil

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Worms do not like compacted soil, in part because they have trouble making their way through it. Soil gets easily compacted when it's wet, so stay off it until it has properly drained. Tillage and digging not only kills earthworms, it also disrupts soil structure and leads to soil compaction. No-till gardening keeps a worm's home intact.

Bare, compacted soil is also an unfriendly environment for worms because compacted soil heats up more quickly than porous soil with a higher moisture content. Grow a cover crop over the winter that you work into the soil before spring planting. This adds nutrients to the soil, reduces water loss from erosion and evaporation, and moderates the soil temperature.

Earthworms need a soil that is relatively pH-neutral, neither too acidic nor too alkaline. It's easy to test your soil's pH. Soil with a pH between 6.0 and 7.0 is conducive to earthworms flourishing.

Keep Soil Moist (Not Wet)

Earthworms can be seen crawling above ground after a rainstorm they can drown in a soil too saturated with water. Pooled water is a sign that you need better drainage. Clay soil drains very slowly, so add compost and other amendments to allow for better drainage. Dry sandy soil is also a generally sterile, hot, and inhospitable environment. A well-balanced loam soil allows for both moisture retention and proper drainage.

Frequently Asked Questions
  • Which worms are bad for plants?

    Worm-like organisms, such parasitic nematodes, or caterpillars of moths, beetles, and butterflies, are bad for plants. Grub worms, cutworms, and horn worms, for example, are caterpillars that feed on live plant roots and leaves rather than dead material. Those that feast on roots remain below the surface of the soil, so unless you dig around for them, you are unlikely to see them.

  • Do earthworms eat plant roots?

    Generally speaking, earthworms will only nibble on plant roots when no other food is available. If earthworms don't have enough dead organic matter to eat, they might start munching on the roots of live plants.

  • Are earthworms good for potted plants?

    Earthworms don't last long in potted plants. They like to burrow deep in the soil and spend their time scavenging, so they need room to move around. And when their food supply of dead organic material runs out, they will start to eat plant roots. To fertilize potted plants with worm castings, cultivate the worms in a worm farm or worm bin, then transfer the castings to your pots.