How to raise composting worms

Raise composting worms to turn vegetable scraps and aged livestock manure into vermicompost for the garden. Use composting worms such as red wigglers (Eisenia fetida), not ordinary earthworms dug from dry soil. They need shade, air, moisture, and small amounts of food; direct sun, flooding, and fresh hot manure can kill them.

Time	About 1 hour to set up; feed weekly; first harvest in roughly 3–6 months
Difficulty	Easy
Cost	KSh 500–2,000 for a small bin, plus composting worms
Location	Anywhere in Kenya with deep shade and protection from heavy rain and midday heat

Before you start

Buy or collect worms from a vermicompost farmer who can identify the species. Red wigglers live and breed in rotting organic matter. Large earthworms from ordinary garden soil usually need deeper soil and may leave or die in a bin.

Start small. A 40–60 litre bucket, basin, wooden box, or opaque plastic box is enough to learn. The bin must drain and breathe, but holes must be small enough to keep out rats and birds.

Fresh manure and fresh grass can heat while decomposing. Age or pre-compost them until the material is cool before it touches the worms. Poultry manure is especially strong; use only a little after it has composted.

Materials

• A 40–60 litre opaque container with a loose lid, or a shallow wooden box
• Composting worms, preferably red wigglers (Eisenia fetida), with some of their old bedding
• Shredded plain cardboard, egg trays, dry leaves, maize stalk fibres, or coconut coir
• A handful of finished compost or ordinary soil for grit and microbes
• Chopped vegetable and fruit scraps, or cool aged cattle, goat, sheep, or rabbit manure
• Clean water
• A sack, cardboard, or breathable lid to keep the bed dark
• Bricks or wood to raise the bin above the ground

Tools

• A nail and hammer, drill, or heated metal rod for holes
• A knife for chopping scraps
• Gloves
• A watering can or bottle with small holes

Safety

• Wear gloves and wash your hands after handling manure, food waste, or vermicompost.
• Do not add human waste, dog or cat faeces, meat, fish, bones, dairy, oil, salty food, chemicals, or plants recently sprayed with pesticide.
• Do not add fresh manure or material that still feels hot inside. Heat and ammonia can kill the worms.
• Keep the bin covered from flies, rats, chickens, and children, but do not seal it airtight.
• Liquid draining from the bottom is leachate, not finished “worm tea.” It may contain harmful microbes. Do not drink it or put it on edible leaves.

Steps

1. Make several small air holes around the upper sides of the container and drainage holes in the bottom. Raise it on bricks in a permanently shaded, well-drained place.
2. Soak shredded cardboard, dry leaves, or coir. Squeeze it: only a few drops should fall, like a wrung-out sponge.
3. Loosely fill the bottom 10–15 cm with this bedding. Mix in a handful of finished compost or soil. Do not press it down.
4. Put the worms and the bedding they came in on top. Cover them with another thin layer of damp bedding and leave them to settle for one or two days.
5. Bury one small handful of chopped food in one corner. Cover it completely with bedding to discourage flies.
6. Check after a few days. Add another small portion in a different corner only when most of the first food has disappeared.
7. Once a week, check the moisture and smell. Mist dry bedding with water. If it is dripping wet, mix in dry shredded cardboard and make sure the drain holes are open.
8. Keep adding thin layers of food and dry bedding. Always leave loose spaces for air and keep the top covered.

Feeding and growing the colony

Good food includes vegetable peelings, fruit scraps, tea leaves without plastic bags, coffee grounds, crushed eggshell, chopped crop residues, and cool aged herbivore manure. Limit citrus, onion, garlic, chilli, and very wet fruit.

Feed by what disappears, not by a fixed calendar. Too much food turns sour and attracts flies. Begin with a small amount once a week; increase slowly as the colony grows. Cocoons and tiny pale worms show that the colony is breeding.

Keep the bed damp but never flooded. Red wigglers work best in mild conditions, roughly 13–25 °C. In hot lowlands, use a shallow bed under a roof, add dry bedding, and check it in the afternoon. In cool highlands, use a thicker bed protected from cold wind. Do not place the bin in direct sun.

Harvesting vermicompost

After about 3–6 months, finished material is dark, crumbly, and smells like soil, with few recognisable scraps.

1. Stop feeding one side of the bin and move the older finished material there.
2. Put fresh damp bedding and food on the other side.
3. Wait one or two weeks for most worms to move to the fresh food.
4. Scoop out the finished side by hand. Return any worms and cocoons you find.
5. Keep the vermicompost in shade. Mix a handful into planting holes or blend it with soil for seedlings; it is an amendment, not a complete replacement for soil.

To expand the farm, divide a healthy crowded bed between two prepared bins. Move worms together with their moist bedding; do not count or wash them.

Common problems

• Rotten smell. The bin is too wet, compacted, or overfed. Remove rotting food, add dry bedding, and open the air and drain holes.
• Worms climb the walls. The bed is flooded, hot, sour, or newly disturbed. Check temperature and moisture; add fresh damp bedding. A few explorers during the first nights are normal.
• Ants enter. The bed is too dry or food is exposed. Moisten it, bury food, clean scraps from around the bin, and move it away from an ant trail.
• Many flies. Stop feeding for a week, bury all food, and cover with 5–10 cm of damp bedding.
• Worms disappear. Look for heat, direct sun, flooding, pesticide residues, or predators before buying more.
• Food remains for weeks. The colony is small, too cold, or overfed. Remove excess and offer smaller chopped portions.

Sources

• Matheri et al., Vermicompost and worm tea production on-farm, FiBL technical guide for farmers and extension staff in Murang'a and Tharaka Nithi, Kenya, 2024.
• Oregon State University Extension, Composting with worms — worm species, bedding, moisture, temperature, and feeding.
• University of Georgia Cooperative Extension, Vermicomposting Basics for Gardens, Landscapes, and Farms — bin care, suitable feed, and harvesting.