Composting worms are different to the earthworms that are naturally found in a healthy garden. Compost worms feed on organic waste at the surface of the soil, whereas earthworms feed throughout the layers of the soil profile, making tunnels deep in the root zone as they go. These tunnels act as a watering service to the deeper soil where the plant roots are. Earthworms’ tunnels aerate the soil and create drainage holes covered in a slimy mucus which helps them move through the earth. This mucous leaves a nutrient-rich residue inside the tunnel that plants access for their growth and vitality. So, no, earthworms from your garden will not thrive in your worm farm. The best thing to do to grow and encourage the earthworm population in your soil is to spread compost worm castings throughout your garden.

Worms feed on the bacteria and fungi that covers food waste and other organic matter to break it down. The decomposition process occurs at different rates depending on the material. Fruit and vegetable scraps work well; ideally cut them up small, so they break down faster. Cereals, grains and carbohydrates work well, either cooked or uncooked. Manures and compost are good, too. Organic materials such as cow and horse manure and compost already contain large amounts of organisms so the worms can process more, faster. However, be careful not to feed your worms manure from animals that have received deworming treatment in the two weeks prior to manure collection.

There are some types of foods that worms don’t enjoy as much and can take much longer to break down, becoming problematic in your worm farm. They can become smelly and could encourage unwanted visitors such as blow-flies or vermin and put the farm out of balance. If your farm does turn ‘sour’ remove all food and mix up the remaining material in the tray with your gloved hands. It can also be helpful to apply a sprinkle of lime or worm farm conditioner. Recommence feeding with more suitable materials. Onion: Very small amounts of onion are OK, but too much can turn a worm farm acidic and unbalanced. Citrus: Takes a long while to break down and worms find it difficult to process. Dairy: It is possible to feed a worm farm a small amount of dairy, however it works best diluted with water; eg yoghurt diluted with water and poured over worm material. This helps disperse the high protein and fat evenly so the worms can eat it before it has a chance to go off. Meat: It is possible to process a very small amount of meat in a worm farm, however it does take time to break down and you would need to bury it deep under the soil in the trays to discourage blow fly larvae.

When starting out a worm farm, about 250 grams or two handfuls of chopped food scraps every couple of days is recommended. To keep the farm well balanced it is a good habit to sprinkle a small amount of compost, soil or straw after each deposit. As your worm population grows, the amount of food you can feed also increases. A tier tray worm farm working at full capacity has the potential to process 2-4 kilograms of food waste every week.