Earthworms are among the most valuable organisms found in many garden soils. Often described as ecosystem engineers, they influence the soil through their feeding, burrowing and production of castings. Depending on the species and its ecological role, an earthworm can help create soil channels, incorporate organic material and support the movement of nutrients through the soil ecosystem.
Earthworms are not simply underground fertiliser factories, however. Their contribution varies with species, soil conditions, moisture, organic matter and the way a garden is managed. Finding one is encouraging because it shows that the soil provides a suitable habitat for that individual, but a single earthworm cannot prove that the entire soil ecosystem is healthy. Understanding these creatures helps us protect the biological processes that support productive gardens.
Written by Kutlwano Mokoena
Founder of Evergreen Hideout Agricultural Services (NPO: 2024 / 380375 / 07). Focused on insect identification, soil biology and ecological gardening.
🪱 First Encounter: A Sign of Soil Life
When we first arrived at Raikana Primary School to work on the garden earlier in 2026, I noticed that the soil did not show much visible worm or other soil-animal activity. Plants were already growing, and the previous gardener had been planting, but the beds appeared to need improvement. Some plants were surviving without showing the vigorous growth I hoped to achieve.
I began working on the garden over the following weeks. I added compost, mulch and other organic matter, watered the beds and continued preparing the soil. I also turned and loosened sections of the garden as part of the work. I wanted to improve the growing conditions, but I knew that changes in soil structure and biological activity would take time.
What I observed: One day, while turning the soil in a bed I had been preparing, I noticed an earthworm moving through the dark soil. It was pinkish, elongated and clearly segmented. I stopped what I was doing and watched it move. I was genuinely happy to see it because I had been putting so much effort into improving the garden.
What I did next: I was wearing garden gloves, so I carefully picked it up and watched it move across my hand. It was fascinating to feel how its body stretched and contracted as it moved. I did not want to injure it; I simply wanted to observe it more closely. After a few moments, I gently returned it to the soil.
🪱 Personal Connection: I had spent weeks adding compost, mulch and organic matter, but I could not immediately see what was happening beneath the surface. Finding that earthworm was an encouraging moment. It showed me that at least one soil-dwelling organism was finding suitable conditions in the bed.
I knew that one earthworm could not tell me everything about the soil, but it gave me a reason to keep observing. It reminded me that soil improvement is not only about what we add to a garden. It is also about creating conditions in which living organisms can survive and contribute to the ecosystem.
This sighting was significant to me for three reasons:
- A sign of suitable habitat: The earthworm showed that the bed provided at least some of the conditions needed by a soil-dwelling organism, including shelter and access to resources.
- A reason to keep improving the soil: Adding organic matter and maintaining suitable moisture can support earthworm populations, although their presence and abundance also depend on species, soil conditions and other environmental factors.
- A lesson in patience: Soil improvement takes time. Changes beneath the surface are not always immediately visible, so continued observation is an important part of gardening.
📍 Location: Raikana Primary School, Soshanguve, Pretoria
📅 Date: 2026
🌱 Garden conditions: Compost, mulch and organic matter had been added over several weeks
🔎 Encounter context: Turning the soil in a prepared garden bed; one earthworm was discovered, briefly observed in gloved hands and returned to the soil
Identification: Understanding Earthworm Anatomy
Earthworms are segmented invertebrates belonging to the group Annelida. They are commonly placed in the class Clitellata, with traditional classifications grouping many familiar earthworms among the oligochaetes. Their long, soft bodies are divided into repeated segments, giving them the flexible appearance that makes it possible to move through soil and other narrow spaces.
The photograph shows an earthworm-like animal with a visibly segmented body. However, identifying the exact species from a general photograph is difficult. Earthworm identification can require close examination of features such as the clitellum, segment arrangement, setae and other anatomical details.
Key identification features
- Body: Elongated, soft and cylindrical, with numerous visible segments.
- Colour: May range from pale pink and reddish-brown to darker brown or grey, depending on species and pigmentation.
- Clitellum: A thicker, glandular band around part of the body in sexually mature individuals. It plays an important role in reproduction and cocoon formation. It is not equally visible in immature worms.
- Setae: Tiny bristle-like structures on many body segments. These help the worm grip surrounding material as it moves.
- Movement: Earthworms move by alternating the contraction and relaxation of circular and longitudinal muscles, extending and shortening different parts of the body.
- No legs or antennae: Earthworms do not have the jointed legs or antennae found in insects.
What is the clitellum?
The clitellum is one of the most recognisable features of a mature earthworm. It appears as a thicker, often lighter-coloured or differently pigmented band around part of the body. During reproduction, it secretes material that helps form a cocoon in which fertilised eggs develop.
Its position and appearance differ between species, so it can help with identification but should not be used alone to determine the exact species. Young earthworms may not yet have a clearly developed clitellum.
Why do earthworms stretch and contract?
Earthworms move using coordinated muscle action. Circular muscles contract to make sections of the body longer and thinner, while longitudinal muscles contract to make them shorter and thicker. Their setae help anchor sections of the body against the soil as the worm moves forward.
This combination of muscles and bristles allows earthworms to move through soil, leaf litter and other suitable habitats without needing legs.
Ecological Role: How Earthworms Influence Soil
Earthworms are often called ecosystem engineers because their activities can change the physical and biological properties of soil. Their influence depends on their ecological group and feeding habits. Not every earthworm creates the same type of burrow or performs the same role.
1. Soil channels and aeration
Some earthworms create burrows that allow air and water to move through the soil. These channels can improve water infiltration and provide pathways through which roots may grow. The effect depends on the earthworm species, soil texture, burrow depth and the condition of the surrounding soil.
2. Organic matter breakdown
Many earthworms consume decomposing leaves, plant residues and other organic material, often together with soil and microorganisms. Their feeding helps fragment and redistribute organic matter. This supports the wider decomposition process carried out by fungi, bacteria and other soil organisms.
3. Nutrient cycling and castings
As earthworms digest organic material and soil, they produce castings. These castings contain mineral particles, organic compounds and microorganisms. Their nutrient content varies according to what the earthworms have consumed and the conditions in which they live.
Castings can contribute to nutrient cycling and soil structure, but they should not be treated as a complete, predictable fertiliser. Their composition is not identical from one worm population or composting system to another.
4. Soil structure and aggregation
Earthworm activity can help bring mineral particles and organic matter together into aggregates. These aggregates influence how soil holds water, drains and resists structural breakdown. The overall result depends on the soil's texture, organic matter content and biological activity.
5. Interactions with soil microorganisms
Earthworms interact with bacteria, fungi and other microorganisms through their feeding and movement. Their digestive systems process organic material and soil, while their casts and burrows create additional habitats for microbial activity. These interactions can influence decomposition and nutrient availability.
Different earthworms perform different jobs
Earthworms are often grouped according to where they live and how they feed:
- Epigeic earthworms: Usually live near the soil surface in leaf litter and decomposing organic material. Many species used in vermicomposting belong to this ecological group.
- Endogeic earthworms: Live and feed mainly within the soil, often creating horizontal or branching burrows while consuming soil rich in organic matter.
- Anecic earthworms: Some species create deeper, more permanent vertical burrows and may pull surface plant residues down into the soil.
These categories help explain why earthworms can have different effects on soil. A compost-dwelling species living in a worm bin does not necessarily perform the same ecological role as a deep-burrowing species in a garden bed.
Are earthworms reliable indicators of soil health?
Earthworm numbers can be useful as one part of a broader soil assessment. Their abundance may reflect factors such as moisture, temperature, food availability, soil disturbance and the presence of suitable habitat. However, a low count does not automatically mean that soil is unhealthy, and a high count does not guarantee that every aspect of soil function is good.
For a more complete assessment, consider earthworm activity alongside soil structure, organic matter, drainage, plant performance, soil cover and other biological observations. The important lesson is to look at the whole soil ecosystem rather than relying on one organism as a single measure of success.
Vermicomposting: Turning Organic Waste into Worm Castings
Vermicomposting is a method of processing suitable organic materials with the help of earthworms and microorganisms. It is commonly used to turn selected kitchen scraps and other biodegradable materials into a stable, soil-improving product.
One important distinction is that not all earthworms are equally suited to vermicomposting. Worm bins generally use surface-dwelling, compost-adapted species, such as Eisenia fetida and related compost worms. These species are adapted to living in rich, decomposing organic material and are different from many of the earthworms naturally found deeper in garden soil.
What are worm castings?
Worm castings are the material that passes through an earthworm's digestive system. They contain processed organic matter, mineral particles and microorganisms. Their composition depends on the feedstock, the worm species and the conditions in the vermicomposting system.
Potential benefits of vermicompost
- Organic matter recycling: Vermicomposting can turn suitable food scraps and plant residues into a useful soil amendment.
- Nutrient contribution: Castings can contain nutrients such as nitrogen, phosphorus and potassium, although the amounts vary.
- Soil structure: Properly produced vermicompost can contribute organic matter that supports soil aggregation and moisture management.
- Biological activity: Vermicompost contains microorganisms that participate in organic matter decomposition and nutrient cycling.
- Waste reduction: A well-managed worm bin can divert suitable biodegradable material from general household waste.
Basic conditions for a worm bin
A successful vermicomposting system needs more than just earthworms and food scraps. Compost worms require a suitable environment in which they can breathe, feed and reproduce.
- Moisture: Bedding should remain moist but not waterlogged. Excess water can reduce oxygen availability and create unhealthy conditions.
- Airflow: The bin needs adequate ventilation and a structure that allows excess moisture to drain where appropriate.
- Bedding: Shredded, untreated cardboard, paper and suitable dry plant material can provide a carbon-rich bedding base.
- Food: Add suitable kitchen vegetable scraps and other appropriate organic materials in moderate quantities. Avoid overfeeding.
- Temperature: Keep the bin within a suitable temperature range for the worm species being used. Extreme heat and cold can stress or kill compost worms.
- Protection: Keep the bin shaded and protected from heavy rain, direct sun and animals that may disturb it.
Vermicompost is best used as a soil amendment rather than assumed to be a complete fertiliser. Its nutrient contribution varies, and plants may still require other nutrients depending on the growing medium and crop requirements.
Protecting Earthworms in the Garden
If earthworms are present in a garden bed, the goal should be to maintain suitable habitat rather than trying to collect or relocate them unnecessarily. A few practical gardening choices can help protect soil organisms.
1. Add organic matter thoughtfully
Use mature compost, suitable plant residues and organic mulches to maintain a supply of organic material. Different earthworm species feed in different ways, but organic matter supports the wider food web on which many soil organisms depend.
2. Maintain suitable soil moisture
Earthworms need moisture to survive because they exchange gases through their skin. Soil that becomes extremely dry can force them deeper into the ground or cause them to become inactive. Water garden beds according to plant needs and soil conditions, while avoiding prolonged waterlogging.
3. Reduce unnecessary soil disturbance
Repeated deep digging and intensive cultivation can damage earthworms, disturb their burrows and disrupt soil structure. Where practical, use targeted cultivation, shallow preparation or less disruptive gardening methods. Some digging may still be necessary, but it should be done carefully when soil organisms are present.
4. Be careful with pesticides and other chemicals
Some pesticides and soil treatments can harm non-target soil organisms, including earthworms. Use products only when necessary, follow the label and avoid applying chemicals indiscriminately to garden beds.
5. Keep soil covered
Mulch and living ground cover can help reduce moisture loss and protect the soil surface from extreme temperature changes. Choose suitable materials and keep them managed around plant stems to reduce the risk of excess moisture and other plant-health problems.
6. Observe before making changes
Earthworm activity varies with season, rainfall, temperature and soil conditions. If you do not see worms during one inspection, it does not mean they are absent. Look for signs such as burrow openings, casts and worms beneath suitable organic cover, while remembering that these signs are not always present.
Frequently Asked Questions
Q: What do earthworms eat?
A: Many earthworms consume decomposing plant material, microorganisms and soil containing organic matter. Their diets vary according to their ecological group and species. Compost worms, for example, feed readily on suitable decomposing organic material.
Q: How do earthworms benefit my garden?
A: Depending on the species, earthworms can create soil channels, process organic material, produce castings and influence soil structure and nutrient cycling. Their activity can support a functioning soil ecosystem.
Q: How can I encourage earthworms in my garden?
A: Maintain suitable moisture, add organic matter, use mulch, reduce unnecessary soil disturbance and avoid indiscriminate pesticide applications. These practices support soil organisms generally, although earthworm numbers also depend on local species and environmental conditions.
Q: Are earthworms harmful to plants?
A: Most familiar garden earthworms are not considered plant pests and generally feed on organic material and soil rather than healthy living roots. However, earthworm species differ, and a worm's presence should not be used to explain plant damage without further investigation.
Q: Does finding an earthworm mean my soil is healthy?
A: It is an encouraging observation, but not a complete soil-health assessment. Earthworm activity depends on moisture, temperature, food availability, soil type and species. Assess soil structure, drainage, organic matter and plant growth as well.
Q: Can I use any earthworm in a vermicomposting bin?
A: No. Many ordinary soil-dwelling earthworms are not adapted to living in a concentrated compost environment. Vermicomposting usually uses compost-adapted species, such as Eisenia fetida, which thrive in decomposing organic material.
Q: Why do earthworms come to the surface after heavy rain?
A: Heavy rain can fill soil pores with water and reduce the availability of oxygen in some conditions. Earthworms may move to the surface to avoid waterlogged soil, although the reasons for surface activity vary between species and circumstances.
Quick Diagnostic Summary
Segmented, elongated invertebrate belonging to the annelid group. Exact species cannot be confirmed from this photograph alone.
Segments, tiny bristles called setae and, in mature individuals, a specialised reproductive band called the clitellum.
Can influence soil structure, organic matter breakdown, nutrient cycling and the wider soil food web.
Maintain organic matter and suitable moisture, minimise unnecessary disturbance and use pesticides cautiously.
Conclusion: The Hidden Life Beneath Our Feet
Earthworms are quiet participants in the life of the soil. Through their feeding, movement and production of castings, many species help shape the environment in which plants grow. Their influence connects organic matter, soil structure, microorganisms and the wider food web.
My first memorable encounter with an earthworm at Raikana Primary School came after weeks of adding compost, mulch and organic matter to the garden. Seeing that worm was an encouraging moment. It did not prove that every part of the soil had recovered, but it showed me that the bed offered a suitable place for at least one of these important organisms.
That experience reminded me that soil improvement is a gradual process. We may not always see the changes happening beneath the surface, but careful observation helps us recognise the signs of a developing ecosystem. Sometimes, a single earthworm is enough to remind us why protecting the life beneath our feet matters.