How to Increase Earthworms in the Garden

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Earthworms are essential for continuously healthy garden soil. They help gardeners get better crop yields and have healthier plants growing in the garden. Many gardeners get frustrated when their soil quality is becoming lower and lower due to a lack of earthworms in the soil. So how do you increase earthworms in the garden? We will answer that question in this post along with why you want to have earthworms in your garden.

Why Earthworms are Important for Healthy Gardens

  • Provide soil aeration.
  • Help with drainage in the soil.
  • Add nutrients to the soil.
  • Help aid root growth of plants.
  • Speed up the composting process.
  • Help increase crop yields.

Earthworms help provide essential nutrients to a garden. They are like tiny little tillers that live in the soil mixing it with rich nutrients by eating, moving around, and leaving castings (aka worm poop).

So if you are wanting to have richer soil then attracting earthworms to your garden is a great idea.

The burrows that earthworms make help provide aeration and aid in the drainage of the soil. Their castings that are left at the entrance to their burrows and within the burrows help provide nutrients that plants can use to grow.

Earthworms also help speed up composting of organic material that is on the surface of the soil. This process can help add nutrients to the soil from their excretions after eating organic matter.

According to a study done in 2014, the presence of earthworms has been shown to increase crop yields by 25%. A harvest of 25% more is hardly something to ignore when trying to grow food and it shows just how impactful earthworms are to agriculture.

Worm Castings

The castings that worms leave behind are like black gold for gardeners.

These castings have microbiological colonies that aid in preventing soil-born diseases that can harm plants and they can help keep away harmful insects.

They provide a nutrient source to plants that are easily accessible and won’t burn your plants as man-made fertilizers can.

Types of Earthworms That Are Good For Gardens

There are thousands of species of earthworms, but for the purpose of gardening there are 3 main categories of earthworm species:

  • Litter Dwellers (Epigeic Species)
  • Topsoil Dwellers (Endogeic Species)
  • Subsoil Dwellers (Anecic Species)

Litter Dwellers are worms that live in the litter or compost at the soil surface. They are nonburrowing and feed on decomposing organic matter. Redworms that are used in vermicomposting are in this category. Without organic matter on the surface of the soil, these types of worms will not survive.

Topsoil Dwellers are the worms that stay in the topsoil up to 1 foot down from the surface. These worms feed on the topsoil and leave castings in the soil as they move through the soil.

Subsoil Dwellers live in the subsoil and are what we commonly refer to as nightcrawlers. They create vertical burrows that can go down below the surface up to 8 feet deep. They come up to the surface to get organic material for food. Sometimes you will see piles of castings at the entrance to their burrows.

Increase Earthworms In Your Garden

Things You Can Do To Increase Earthworms In Your Garden

There are a number of things you can do in and around your garden that will help encourage more earthworms to be in your garden.

Add Compost and Organic Matter On Top of Soil

Use compost in the garden to attract earthworms.
Use compost in the garden to attract earthworms.

Compost will provide the organic matter that worms want. By using compost in addition to leaf litter and other organic material you create an environment rich in worm food.

You can buy compost already made or you can make your own compost with a tumbler or a DIY Compost pile.

Using organic mulches and organic matter (coffee grounds, leaves, grass cuttings etc) to cover the soil surface will help allow the soil to retain moisture.

This will also help keep big temperature variations in the soil from happening too. Worm populations will die off during the peak of summer when temperatures get high. But they leave eggs that will hatch in the fall when temperatures cool down.

Reduce Deep Tilling

Reduce tilling in the garden

If your goal is to increase the number of earthworms in the soil of your garden then reducing deep tilling is one of the best things you can do for your garden.

Tilling disturbs the soil that the worms live in and can damage the delicate ecosystem that goes on within the top layer of soil. It can also kill worms already in the soil that is being tilled.

Instead of tilling the soil, you can just add compost to the top of the soil as described below when using no-dig gardening.

If you don’t want to completely stop tilling your garden, at least only do shallow tilling.

The deeper you till the more harm you can bring to earthworms. Shallow tilling will allow the management of surface litter above the soil. Tilling the surface liter can actually lead to an increase in the activity of earthworms.

Use No Dig Gardening

With no-dig gardening, you are providing organic matter and adding compost on top of the soil. This provides a great environment to encourage the worm population to grow in the area.

Use Cardboard Instead of Landscaping Fabric

Often gardeners will use landscaping fabric in areas where they don’t want weeds to grow. This could be in flower beds or in garden paths.

Using cardboard instead of landscaping fabric can provide a natural material that will smother out weeds and worms love cardboard.

Yes, you will have to reapply more cardboard to the area over the years. But I have yet to use a landscaping fabric that actually keeps out the weds and doesn’t need to be replaced every few years.

While it might be a small extra amount of work in the long run, you are providing an environment that encourages earthworms to live in and around your garden. And you also get the bonus of finding a use for all of those Amazon boxes that keep arriving.

Pay Attention to What You Use in Your Garden

Avoid Harmful Chemicals in the Garden

Pesticides, fertilizers, and some fungicides can be harmful to earthworms.

Stay away from pesticides that contain aldicarb, carbaryl, carbofuran, and benomyl.

Even some fertilizers can cause harm too. Fertilizers that contain ammonium sulfate can reduce earthworm populations.

Use Cover Crops

Using cover crops has been shown to increase earthworm population three times higher than not using cover crops.

In addition to increasing earthworm numbers, cover crops also increase nitrogen levels in the soil and the microbial biomass.

Maintain Moisture Levels

Earthworms need moisture, if they dry out they can die. But they also don’t like to live in soil that is drenched and retaining water. So maintaining even moisture levels in your soil is important.

When it gets too dry, earthworms will go down to lower levels in the soil where they can find moisture. If they can’t find the moisture they will enter a hibernation state to protect themselves.

Do coffee grounds attract earthworms?

Coffee grounds can help attract earthworms to the garden. You can place coffee grounds in your compost pile/bin or you can lay used coffee grounds on the top of the soil. If you place coffee grounds directly on your garden, make sure they are used coffee grounds and don’t put more than an inch high. Too many coffee grounds can be harmful.

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