How to Add Worms to a Garden

Earthworms play pivotal roles improving soil structure and aiding plant growth, and adding earthworms to your garden or raised beds can mirror their natural contributions to soil health and plant life.

In this article, we explain the science behind adding worms to soil and highlight everything you need to know to get the most out of worms in your garden or raised beds.

Can You Add Worms in Your Garden and Raised Beds?

The simple answer is yes - earthworms can be added to your garden and they can perform the same essential roles in your garden that they do in nature. Decades of scientific studies have shown that having earthworms in soil significantly enhances soil health and plant growth, leading to higher yield, larger plant biomass, and a host of pest and disease benefits. 

More specifically, worms do all of the above in 2 important ways:

• They burrow in the garden soil, contributing to improved aeration and drainage. These drainage burrows help get air and water to root systems and are proven to result in larger root masses for plants.

• They enhance soil fertility with worm castings, which are rich in biology (think nematodes and protozoa) that aid in the cycling and release of nutrients that plants need. In other words, worms leave behind poop (castings) alive with tiny organisms that munch on organic matter (and one another!) to release the food plants need to grow.

How Many Worms Should I Add to My Garden?

Determining how many worms to add to your garden is part science and part art - you don’t need a dense population of earthworms per square foot if your goal is to add aeration and biology to your soil. Based on our experience a good guideline is 1-5 worms per square foot. So if your garden space is 800 square feet then 1,000 - 2,000 worms will be a great start. The worms will breed and over time their population should grow as long as soil conditions are good.

The art of adding worms is as important as the number of worms - worms need to find one another to breed and populate, so rather than spreading 1-2 worms every square foot in your garden or garden bed, we recommend adding all of the worms in 1-2 areas of your garden or raised bed.

This approach allows the worms to find mating partners, and over time the population will expand to other areas of your garden or raised bed.

What kind of worms should I add to my garden

The most beneficial types of worms to add to gardens are typically red wigglers (Eisenia Fetida) and European nightcrawlers (Eisenia Hortensis). These species are close genetic cousins, with similar physical appearance. The main difference between the species is that the nightcrawlers are ~ 50% bigger than red wigglers.  Both species feed in the top 2-3 inches of soil and are good at digging tunnels in the soil and leaving behind worm castings that benefit garden soils and plant growth. 

Red wigglers are more tolerant of higher and lower temperature ranges than European nightcrawlers (ENCs), so they are generally the best option for most climates. 

Red wiggler - voracious eater and breeder

It is also worth noting that ENCs are “anecic”, meaning they are a burrowing worm that digs deeper into the soil (12-15 inches) than red wigglers (2-3 inches). However, science has shown that there are benefits to having either species and they essentially perform the same function. 

How to Add Earthworms to Your Garden

Adding earthworms to your garden or raised bed is straightforward - simply place them on the surface of the garden or raised bed or dig a small hole for them. Worms do not like sunlight so they will burrow into the soil within a few minutes or few hours. Keep in mind that earthworms thrive in moist, rich, and organic matter-heavy soil, and they need a food source (e.g., decaying organic matter like leaves) to survive.

If your soil is too sandy, clay-heavy, or lacks organic matter, consider amending it with organic compost, aged manure, or leaf mold to increase its appeal to earthworms.

It's also a great idea to moisten the top layer of the soil before adding worms to your garden or raised bed.

When Should I Add Worms to My Garden

The best time to add earthworms is either early morning or late evening. Make sure the area is moist and gently dump the worms on the soil surface or dig a shallow trench to place them in, then cover them with soil, compost, or organic mulch. This approach provides the worms with immediate shelter and food sources.

How to Keep Worms in Your Garden

As your garden grows and leaves and dead fruit or vegetables fall into the ground, worms will consume the decaying organic matter so this will be a good food source for them as well. 

Note that worms never eat living organic matter like roots plants, or vegetables, so they will only consume dead and decaying material.

Avoid using chemical pesticides and fertilizers, which can harm earthworms. We also do not recommend store bought compost or mulch, as it can be treated with chemicals that can harm worms.

Finally, tilling will kill worms so if possible a no till approach is your best option for keeping worms alive and happy.

Frequently Asked Questions: Adding Worms to Your Garden

What Worms are Bad for the Garden?

Most earthworm species are beneficial to garden soil, where they happily coexist with plants and roots while contributing to nutrient cycling, aeration, and soil porosity. However there are certain types of invasive worms like the Asian Jumping worms that should be avoided or removed from your garden. Asian jumping worms are redddish brown, 6 or more inches long, and have a flat clitellum around their neck area.

We recommend sticking to common composting worms like the red wiggler when adding worms to your garden or raised bed.

Can You Add Earthworms to Potted Plants?

Yes, adding earthworms to potted plants can be beneficial, but adding worm castings is generally a better option for potted plants. Worm castings offer the biological and nutrient cycling benefits without the drawbacks of keeping worms alive in a small container.

Can I Put Red Wigglers in My Garden?

Yes! Red wigglers are a great earthworm option for your garden or raised bed and are the best worm to add to most gardens. Red wigglers are a hardy worm that can survive in a wide range of climates and temperature ranges, and they are active composters and breeders. This combination makes them a great choice for aerating and adding nutrients to garden soils.

Can I Add worms to Potted Plants?

Worms can help aerate soil and produce castings that will help potted plants in the same way worms aid plant health in nature. However, success with putting worms in potted plants depends on the size of the container (larger is better), a food source for the worms, and using organic potting soils that won’t harm the worms. For more check out this article on adding worms to potted plants along with alternatives that work just as well!