Garden and food waste

Worm farming

What is worm farming
Getting started
What worms eat
Harvesting your worm casts
Common problems
Where to buy worms and worm bins
Types of worm bins

What is worm farming

Compost can be produced using worms and your kitchen food scraps. This is known as worm farming. It is also called 'vermiculture' or vermicomposting.

Tiger worms are usually used in New Zealand, though red worms can also be used.

Worm farming uses the same principles as composting, but does not generate heat, making it cold composting. Value is added to the materials when they are eaten and excreted by the worms. This produces what is called vermicast and worm tea which have high levels of nitrogen, phosphorous and potassium (NPK) compared to ordinary soil. This makes them valuable for your plants' leaf growth, root and stem strength and flower and fruit set.

Worm farms don't need much space so are ideal if you only have a small backyard.

The benefits

	Casts and worm-tea are fantastic for plants (always dilute the worm-tea to the colour of weak tea - usually about 1:10)
	Kids enjoy them
	If you have mostly kitchen waste and live in a home with little or no outdoor space, a worm farm is a good option
	All of the same benefits as regular composting.

Getting started

	Choose a site which is sheltered from sun, wind and rain. Carports or sheltered porches are ideal
	Use a layer of bedding first - eg. hay, coconut fibre, shredded cardboard or paper
	Bedding should be damp and porous
	Add worms - 1000 (250 grams) is fine; 2000 is even better
	Food can then be added. You can cover food scraps with damp newspaper or cardboard to limit flies and odour
	Worms can eat their own weight each day but don't overfeed at start (eg. for 250 grams of worms give about 200 grams of food
	Worms need air but not light (worms are photophobic).

Worms at work: a population of 1000 to 2000 worms is needed to get started.

Keeping it going

	Worms need a moist environment
	Check that their surroundings are damp, add water if needed
	Add dry leaves or torn up paper products if it is too wet - the working area should be as damp as a wrung out sponge
	Add food scraps regularly
	Smaller pieces (no larger than 2cm) will be eaten more quickly and prevent odours
	Worms cannot tolerate very hot or cold conditions (10 to 30 degrees is OK)
	Small flies or white worms/bugs indicate the worm farm has become too acidic and you should add a sprinkling of lime to neutralise pH
	Worms are omnivores and will eat almost anything, but some things are best avoided
	If worms are overfed, uneaten food will rot.

What worms eat

What worms like		What worms don't like
	Most fruit and vege scraps		Spicy food, chili, onion, garlic
	Coffee grounds and teabags		Meat and milk products
	Aged horse manure		Flour products
	Dirty paper		Large amounts of cooked food
	Crushed eggshells		Garden waste
	Vacuum cleaner dust		Shiny paper
	Hair		Citrus/very acidic food

Harvesting your worm casts

	After a few months or when a layer is full, you should harvest the casts.
	Remove the top layer and take off the bottom layer. This bottom layer contains the casts. It is ready when few worms can be seen.
	Remove worm tea from the bottom level. (When using, dilute to the colour of weak tea, usually about 1:10)
	When one working layer is full, you can add another layer to your worm farm.
	Place new layer on top of the old one and then add bedding (paper/ straw/ manure) and then add more food scraps.
	Add food only to the new layer. The worms will migrate slowly to the food layer.
	If you have large layers in your plastic bin and you want to harvest casts earlier, you could add a layer of chicken wire instead of a new plastic layer.

Worm casts ready for use (left) and view from the top with worm tea in the bucket below.

Common problems

Problem	Cause	Solution
Rotting food	Too much for population	Feed less
Fruit/vinegar flies around farm, or small white bugs and worms	Too acidic	Cover food with damp paper. Add lime to increase pH
Worms climbing up sides or worms very fat and pale	Too wet	Add paper products and dry leaves, gently fork holes in the working layer
Ants	Too dry or acidic	Add water/lime. If your worm farm is on legs, place each leg in a container of water to stop such pests from getting in
Food rotting and not eaten	Too much or wrong food/pieces too big	Add less food, break into small pieces
No worm tea	Not enough water	Add water

Where to buy worms and worm bins

Worm bins can be purchased from various outlets including your local garden or hardware store. Look in the Yellow pages under 'Worm farming' and call first to get an idea of products and prices

Alternatively you can visit the following websites for information:

Types of worm bins

Worm bin showing layers

There are different types of worm bins but most have a number of layers. Note that it is easier to harvest worm casts from bins which have more shallow layers. Bins generally have two to three layers; some bins can have extra layers added to increase capacity. When buying a bin, ask the retailer whether there is any back up if you need advice.

	A tray/layer/stacker system allows for easy removal of worm casts
	Bins with taps allow the worm tea to be extracted easily
	Some bins stand on legs which can be easier to proof against pests (legs can stand in bowls of water if need be)
	Some bins are made from recycled plastic and made locally
	Sizes vary and costs vary between $20 and $200
	Worms and food scraps are added to the top working tray which generally has a vented lid
	More levels can be added once the first working tray has filled with worm casts
	A three-tray system allows for easy removal of worm casts with minimal loss of worms
	Size, price and functionality vary a lot, so ask questions and think carefully before you buy.

Reviewed - March 2007.