Friday, 1 March 2013

Home Scale Worm Farming with Eisenia fetida

Making a Small Indoor/Outdoor Worm Farm (the easiest way)

How would you like some pets that will eat your waste and feed your plants, don't require walking or a babysitter when your away, are extremely quiet and will only ever deposit excrement in the right place. Sounds good...? then look no further then the humble earthworm. Unfortunately they are not so great to cuddle up with.



Worm husbandry is a simple way of turning kitchen and garden waste into a great potting soil or soil amendment known as vermicompost  for use in the garden or on your house plants.

 To name but a few benefits of vermicompost.....
  • Microbial activity in vermicompost  is 10 to 20 times higher than in the soil and organic matter that the worm ingests. This microbial activity ultimately provides mineral nutrients to plants.
  • Improves water holding capacity of the soil 
  • Enhances seed germination, plant growth, and crop yield
  • Improves root growth and structure
It will also provide you with a regular supply of worms to feed to chickens or to populate your garden and if like to fish you will never be short of bait.

What you need

  • Container of wood or plastic. You can use a sturdy plastic container that is about 15 cm deep, 30 cm wide and 45 cm long. These measurements are not critical but you want something with a large surface area that is quite shallow as the worms used for vermicomposting are natural surface feeders (see below).     
  • Worms. The worms we use for vermicomposting are a European native called Eisenia fetida. In natural conditions these worms live in the top soil and duff layer on the soil surface. These small, deeply pigmented worms have a poor burrowing ability, preferring instead an environment of loose organic litter or loose topsoil rich in organic matter. They feed on the organic surface debris.

  • Bedding material. Start with some shredded newspaper, moistened, not soaking wet. Add a couple of handfuls of damp garden soil, and a couple of crushed egg shells (calcium is essential for the worms to reproduce), vegetable and fruit scraps and any herbaceous plant material, fresh or old, cut into small pieces.

What to do

  • Place the damp shredded newspaper with the damp garden soil , crushed egg shells and veggie scraps in the container, mix it up and make sure its all moist, like a wrung out sponge. 
  • Put the worms in. The worms will eventually eat all of this material and by passing it through their gut they transform it into a very high value plant food.... voila,  vermicompost.  
  • Worms do not like light so cover the top of the box with a dark cloth.
  • If you have your worms inside your house/apartment it is worth having a mesh cover or a lid (with air holes) to keep the insects out. 
  • Make sure that you keep the worm farm moist and add more food as the material starts to disappear. You can keep it moist by spraying water over it. Do not add to much food as this can lead to odour problems.
What to feed them 
  • Vegetable scraps and starchy scraps, like bread, oatmeal, and pasta.
  • Soaked paper and cardboard. 
  • Leaf litter and chopped up herbaceous plant material (don't use plants from the Allium familly)  
  • If you really want to treat them, apparently they love bananas. 
  • By blending your kitchen scraps together the worms will process it much quicker. 
  • Do not feed them acidic foods, like citric fruits and they don't like onions or garlic. 
  • If you want to keep the rats away then do not feed your worms meat, poultry, dairy products, or salty food, like potato chips. 
As remarkable as the worms are at processing your scraps do not expect to notice anything special happening in your worm farm immediately but rest assured the magic is going on. Just make sure the material in the worm farm is always moist and keep the food coming at an appropriate rate.

How to harvest

One day you will notice the bedding you put in is no longer identifiable, the consistency of the material will be thick and clay like. Now is the time to harvest the castings.
To harvest your castings.....
  • Start feeding on the surface of one half of your container. Do this for about a week. The worms work out where the food is and migrate to the side of the farm with the food . 
  • Once the worms have migrated, take the black clay like castings out from the end of the farm where you were not feeding them. There may be a few worms in there but this is not a problem.  
  • If the castings are wet then allow them to dry and then sieve the material to remove any matter that has not yet decomposed.
  • The castings you have harvested can be mixed with 50% sand to make an excellent potting medium. You can also apply a handful of the mix when planting out your spring vegetables. 
  • Add new food for the worms and mix this up with the remaining half of the container contents.

Worm care

  • Worms require oxygen so keep the lid partially open to allow air to circulate. 
  • Turn the bedding with a trowel periodically to improve air circulation in the farm.
  • Worms will function best at room temperature. Keep the farm temperature between 7C-29C. 
  • When keeping worms outside, if the worm farm freezes your worms will die but do not throw the medium out. The worms will have laid small oval shaped cocoons in the bedding. The pale yellow ones are newly laid and they turn darker brown when they are ready to hatch. Each cocoon may contain up to 25 baby worms, as the weather warms they will hatch after a few weeks. Look out for tiny white worms.
  • Poultry egg shells added to the bedding will provide calcium the worms need to reproduce. 
Worm cocoons
This is a small domestic version but it can be scaled up to process more waste and breed more worms. If you are building a bigger worm farm outside it would help to have drainage in the worm farm to allow water via rainfall to drain without flooding the worms. The drained liquid from the worm farm is very rich in nutrients and makes an excellent liquid fertilizer. This liquid can be diluted 10 parts water to 1 part worm farm liquid and applied to your plants.

For more info on the ecology of worms click here 


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