Documents: Garden Design:

Vermicomposting (Worm Composting)
by Julie Ferraro
by Julie Ferraro

November 14, 1999

Several months ago I searched for yet another "nature" project for my children to get involved in. I noticed that the children were constantly watching the earthworms outdoors, in that familiar child's squat that marvels us all, helping the stray worms in the garage back into the gardens. That prompted me to try composting with worms, also know as vermicomposting, from vermes, Latin for worms.

Vermicompost, or worm castings, is made in a container filled with moistened bedding and redworms. Add your food waste and the worms and micro-organisms will eventually convert the contents into rich compost. There are many benefits to worm composting. It is perfect for apartment dwellers who don't have yard space, great for children, who love keeping hundreds of wigglers as pets, (they will be the quietest and cleanest pets you're ever had), it will decrease your food waste and the castings the worms produce make an incredibly rich, dark, earth-smelling fertilizer. It is organic, non-burning and rich in nutrients. Another advantage is that it can be done indoors and outdoors, allowing year round composting.


Containers can be either wood or plastic. Wood is more absorbent; plastic tends to get quite wet needing more drainage. Ready made worm bins can be bought, or you can make a bin yourself. Aeration holes should be cut into the top and drainage holes into the bottom, with screening laid inside the bottom of the bin to prevent the bedding and worms from draining out. The bin should be raised with a drainage tray placed at the bottom. If you find one bin isn't enough, a few smaller bins are better than one big one for easier lifting, moving and storing. containers A good size for a bin is 12" high x 16" deep x 24" long.


The worms require a damp bedding to live in, in which you will bury your waste. Materials that can be used are shredded newspaper (the worms will eat this too, so avoid coloured inks) and cardboard, shredded fall leaves, chopped up straw, sawdust, peat moss, compost and aged manure. Try to vary the bedding in the bin as much as possible, to provide more nutrients for the worms and to create a richer compost. Moisten the dry bedding materials before putting them in the bin. It shouldn't be too wet, about the same as a wrung-out sponge. The bin should be about three-quarters full.


Two types of worms can be used; the "red wiggler" or manure worm (Eisensia foetida), or the "red worm", another manure worm (Lumbricus rebellus). Do not use dew worms as they are not likely to survive indoors. For each cubic foot of worm bin, plan on using a half-pound of red wigglers (about 500). You can start off with less worms, putting in less food until the population increases. The worms will multiply rapidly.

Feeding Your Worms

Worms will eat food scraps such as potato peels, lettuce, celery, apples, banana peels, grapefruit and orange rinds, tea leaves, tea bags, coffee grounds, and paper filters. Do not compost meats, dairy products, oily foods, and grains because of problems with smells, flies, and rodents. To avoid fruit fly and odour problems, make sure to bury the food by pulling aside some of the bedding, dumping the waste, and then covering it up with the bedding again, placing the waste in different locations in the bin each time. Eggshells are essential to keep the bedding from becoming too acidic for the worms. Dry the shells well, crush them and sprinkle the tiny pieces over the top of the bedding once a week.

Harvesting Your Compost

It is important to separate the worms from the finished compost approximately every three months, otherwise the worms will begin to die. There are a few different techniques. One way is to move the finished compost over to one side of the bin, place new bedding on the opposite side and bury food waste in the new bedding only. The worms will gradually move over, in about 3 to 4 weeks, to the new bedding, then the castings can be harvested . Another method is to dump the entire contents of the bin onto a large plastic sheet , make tiny mounds, then shine a bright light over the mounds. The worms hate the light and will crawl to the bottom of the mounds. You can them harvest the compost returning the worms at the bottom back to the bin with fresh bedding. Most children love to help with this process and you can turn it into a fun lesson about the worms. You may notice tiny lemon-shaped worm cocoons which contain between two and twenty baby worms. Return them to the bin as well. If your worms have multiplied substantially, start another worm bin with the extras or give them away to others who may want to do so.


Container Plants: Castings can be added to the soil of your potted plants.

In the Garden: Castings can be used directly in your garden as a mulch, dug into the soil, or in the bottom of seed rows.

Seedlings: Castings can be combined with potting mixes for seedlings.

Transplants: Castings can be used as a fertilizer to get your transplants off to a good start. The next time you are transplanting, just throw a few castings in the bottom of the hole before planting.

Worm Compost Tea: Put 2 cups (250 ml) of castings to one gallon (4 litres) of water in a burlap bag, cheesecloth, or old pillowcase. Let it steep in the water for 24 hours. If necessary, dilute it to the colour of weak tea. Water your plants with this very rich nutrient tea. Spread the solid contents in your garden or return to compost pile.

Common Problems

If you find a strong odour coming from the bin it is most likely from overloading the bin with food scraps. The food sits around too long and the contents become too wet, causing a lack of oxygen in the compost. The lack of oxygen causes the odour. Stop adding food scraps until the worms and micro-organisms have broken down the food, gently stir up the contents to allow more air in and stop adding food waste for a week. Worms may crawl out of the bedding and onto the sides and lid if conditions are wrong for them. If the moisture level seems all right, the bedding may be too acidic, You can adjust the pH level by adding a bit of calcium carbonate such as garden lime and cutting down on the amount of citrus peel and other acidic food waste. Fruit flies can be an occasional bother. Avoid them by always burying the food scraps. Keeping a plastic sheet or sack on the top of the compost in the bin can help eliminate them as well.

After an initial week of my 3-year-old son insisting on opening the lid to watch the worms, our project is turning out well. The children enjoy feeding the worms, separating the worms from the compost and making new bedding. They have learned much about worms, and our plants never looked better!

For local sources for redworms and/or bins, look under Environmental Consultants & Services in the yellow pages. Or for mail order companies, look under Worm Farmers in a search on the Internet. In Barrie, Ontario, they can be purchased at:

Environmental Action Barrie, (705) 727-4000

For additional information, visit and read the following excellent website and book:

The Burrow:

Worms Eat My Garbage, by Mary Appelhof

by Julie Ferraro

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