Getting started
Setting up your worm container
- This can be plastic, wood or metal. Use your imagination and recycle an old bathtub, wooden box, drawer or plastic bin
- You can buy ready-made worm bins from garden centres
- Wooden containers provide good insulation but plastic containers are lightweight and convenient
- The container should be at least 20-40cm deep with a surface area of about 40x60cm
- Drill or punch about ten holes of 10mm diameter in the bottom of the container for aeration and drainage - worms need air to live. If contents become too wet, drill more holes. Bins should be raised up on bricks or wooden blocks to help air circulation and drainage
- Loosely cover the bin to keep in the moisture and provide a dark environment for the worms
- Indoors, use sacking or similar material on the compost surface or black plastic sheeting on top of the container
- Outdoors, use a lid or cover to keep out scavengers, predators and the rain
Choosing your worms
Worms live wherever a good supply of organic matter is available. You can check compost heaps for worms, visit horse stables or a farmer with a manure heap and collect the worms there. Otherwise refer to your Yellow Pages under Worm Farming for suppliers of worms.
Two species are especially suited for worm composting - tiger worms, Eisenia fetida, and red wriggler or manure worms, Lumbricus rubellus. These worms thrive on moist organic materials such as food scraps, eating as much as their own weight per day! For a typical family of four, use between 1,000 and 2,000 worms.
Setting up the worm bed
Worms need moist bedding in which to live and lay their eggs.
Suitable materials include:
- Moistened newspaper torn into 25mm strips (avoid coloured print if possible)
- Cardboard
- Peat
- Straw
- Aged manure
- Compost
Experiment with different materials – a mixture of ingredients is okay. Fill three quarters of the bin with bedding that has the consistency of a squeezed out sponge.
Add one or two handfuls of coarse sand or topsoil. This provides the grit that worms need to grind their food.
What to feed your worms – good and bad food
Worms eat plant and meat tissue, so most organic kitchen waste can be composted. Here’s a list of what you should and shouldn’t feed them.
Good worm food:
- Vegetable and fruit scraps or peelings
- Shredded paper or paper towels
- Tea bags or leaves /coffee grounds and filters
- Egg shells
- Bread and cereal
- Plate scrapings - all leftovers, even ice cream!
- Meat and fish scraps and dairy products
Bad worm food:
- Citrus or acidic fruits such as oranges, lemons, grapefruit and kiwifruit
- Garden waste (better in your normal compost bin)
- Fats, cooking/salad oils and oily foods
- Tough woody material unless chopped into small pieces
- Onions, garlic or hot spicy food scraps
Remember worms don’t like bones, glass, plastic or tin foil.
Harvesting the compost
After three or four months the food waste turns into worm compost, ready to be used on your garden. This means it's time to harvest.
The easiest way to do this is:
- Scoop out the top 150mm layer (this is where the worms are), and set it aside for a new bin
- The compost can then be easily removed and used on your garden
- Put the top layer back into the container with fresh bedding and start a new worm farm
Be careful that the worms don't dry out and watch for baby worms and the tiny oval-shaped cocoons, which may contain baby worms.
Using the compost
Worm compost is nutrient rich and is an excellent material for using directly on container plants or combining with potting mix. It can also be used every time you plant – mix a handful into the soil.
Worm tips
- Worms need to be kept moist but not soggy. If they dry out they will die, or if it's too wet they will drown
- Kitchen food waste is generally pretty moist. To prevent sour and slimy conditions (creating odours and attracting flies), add food regularly rather than in large quantities
- Chopping or mincing food scraps speeds up the process
- Crushed eggshells normally provide enough calcium to stimulate worm reproduction, but a monthly sprinkling of dolomite or garden lime will help
- Make sure food is buried in the bedding to avoid fruit and houseflies
- If your worm farm gets smelly, this might mean the worms have been overfed, the bin has become too moist, or the bedding has become packed down, limiting airflow
- Watch out for food with seeds such as pumpkins or tomatoes. As worm composting doesn't generate heat, seeds may start growing!