Skills books › Composting, Worm Farming and Healthy Soil in South Africa

How to start a worm farm

Composting worms turn kitchen scraps into the richest compost there is. They need dark, damp bedding, air, food and shade. Keep them out of the sun and out of standing water, and they will do the rest.

Use composting worms, not garden earthworms

The earthworms in garden soil burrow deep and do badly in a box. Composting worms live in the top layer of rotting leaves and manure, eat a great deal and breed fast. The two most common in South African worm farms are:

• red wigglers: small, red and tough across a wide range of temperatures;
• African nightcrawlers: bigger, fast eaters that like warmth and do poorly in the cold.

Buy them by weight from a worm farmer or a gardener with a healthy farm. One kilogram is roughly 2 000 to 4 000 worms.

What worms need

• Darkness. Direct sun kills them.
• Moisture. Bedding should be damp like a wrung-out sponge. Worms drown in standing water and dry out in dry bedding.
• Air. A farm needs holes. It must not be airtight.
• The right temperature. They work best at about 15 to 25 °C and die above about 30 °C.
• Food. Raw vegetable and fruit scraps, tea leaves, coffee grounds, crushed eggshells, paper and cardboard.
• No poisons. No meat, dairy, oil, salty or spicy food, and little onion or citrus.

Kinds of worm farm

• Stacking trays with holed bottoms on a base with a tap. When the working tray is full, a new tray with fresh bedding and food goes on top, and the worms move up, leaving finished castings behind.
• A single bin with a lid and holes. It is simple and cheap, but harvesting takes more sorting.
• A larger raised bed with a lid, in the shade, for a school or smallholding.

Never use an old fridge or freezer. A child can climb in and be trapped.

Make your own from two bins

1. Drill rows of 6 mm holes in the bottom of the top bin, and a few air holes near the top of its sides and in the lid.
2. Stand the top bin inside the bottom bin on a few bricks, leaving a gap where liquid can collect.
3. Fit a tap near the bottom of the lower bin, or tip it out now and then.
4. If ants are a problem, stand the farm on bricks set in dishes of water.

Use only containers that have never held chemicals.

Bedding and adding the worms

Good bedding is shredded newspaper or cardboard that has been soaked and squeezed out, soaked coir, or old compost, with a handful of garden soil.

1. Fill the working tray 10 to 15 cm deep with fluffy, damp bedding.
2. Tip the worms on top and leave the lid open in dim light for a few minutes. They will burrow down.
3. Feed only a small handful of chopped scraps in the first week.
4. Cover the surface with a damp sheet of newspaper or sacking.

Start small. Overfeeding is the commonest cause of a smelly farm.

Where to put it

• In deep shade all day: under a tree, on the south side of a building, or in a garage or carport with air.
• Out of the rain, or under a lid.
• Sheltered or covered with old blankets in a Highveld winter.
• In the coolest spot you have in a hot summer, with wet sacks over it on very hot days.
• Out of reach of chickens and rats.

In a South African summer, heat kills more worm farms than anything else. Shade comes first.

This guide is based on Chapter 7 of Composting, Worm Farming and Healthy Soil in South Africa. The next chapter covers feeding worms and harvesting castings.