We’re feeling very lucky right now. Our friends Cherrie and Silva have given us a full vermicomposting setup, worms and all. Thank you so much! So, we thought we’d take this opportunity to share with you everything we know about vermicomposting, worm bins, and worms. Exciting right? Or maybe you’re thinking we’ve lost the plot a bit and have a few questions to assess our sanity? Well, let’s see what we can do about that…

What is vermicomposting?

The simple answer is using worms to convert organic waste into compost. The resulting compost is also known as worm compost, vermicast, worm castings, worm humus or worm manure.

Why would you use worms to compost?

Well there’s more than a few reasons. Worms speed up the composting process, aerate the organic material in the bin, and enhance the finished compost with nutrients and enzymes from their digestive tracts:

Good Bacteria: Vermicompost consists mostly of worm casts (poop) plus some decayed organic matter. In ideal conditions worms can eat at least their own weight of organic matter in a day. In fact it seems they don’t actually eat it — they consume it, sure enough, but what they derive their nourishment from is all the micro-organisms that are really eating it. And yet their casts contain eight times as many microorganisms as their feed! And these are the micro-organisms that best favor healthy plant growth. And the casts don’t contain any disease pathogens — pathogenic bacteria are reliably killed in the worms’ gut. This is one of the great benefits of vermicomposting.

Minerals and other goodies: Worm casts also contain five times more nitrogen, seven times more phosphorus, and 11 times more potassium than ordinary soil, the main minerals needed for plant growth. The casts are also rich in humic acids, which condition the soil, have a perfect pH balance, and contain plant growth factors similar to those found in seaweed. There’s nothing better to put in your garden!

Small location versatility: Prefabricated vermicompost bins are extremely versatile in terms of location. They can be kept in a space as small as a balcony without attracting flies, giving off odor, and looking unsightly. They’re even used indoors.

Great. So how do I vermicompost?

The main components of a vermicomposting system are:

  • housing
  • bedding
  • food
  • worms

Housing: This can be either a prefabricated worm bin, or a self-made version, the purpose of it is to house your worms and contain the composting process.

Bedding: Fill the box with moist bedding for the worms to burrow in and to bury the food scraps in. Worms will eat the bedding as well as the food scraps, so you’ll need to top it up in a few months. Any inert, non-toxic, fluffy material that holds moisture and allows air to circulate will do, things like:

  • Cardboard: cut into strips around an inch wide and a few inches long. (don’t use the shredded cardboard sold for insulation because it’s treated with toxic chemicals.)
  • Newspaper: tear it into 1″ strip. Avoid glossy paper.
  • Shredded computer paper.
  • Autumn leaves: Shred them with a lawnmower. Or moisten them, sprinkle some lime, ground limestone or wood ash over them and bundle them up in a garbage bag, tie the top closed, and in a few months they’ll have broken down enough to be excellent worm bedding. Or just use them as is, though it’ll take a bit longer for the worms to break them down.
  • Aged manure, or composted manure: cow, horse, rabbit.
  • Sphagnum peat moss: soak it in water for 24 hours, squeeze it out and sprinkle some lime on it.
  • Coco peat moss or coir (coconut fibre): comes in compressed bricks, soak in water and they swell up — no need to add lime.
  • Chopped-up straw or other dead plant material, spoiled hay, yard clippings, dried grass clippings: any plant material “aged” beyond the green stage.
  • Sawdust, wood shavings: from non-aromatic wood, avoid treated wood, about a quarter to a third of the bedding mixture.

Add a couple of handfuls of soil or sand — it helps the worms grind up the food in their gizzards. Sprinkle a bit of lime, ground limestone or wood ash over the bedding (not too much!). Ground limestone is best. Once it’s all suitably shredded, mixed and moist, put it in the box and add the worms. Leave it for two or three days to let the worms settle in before adding wastes.

Food: This is made up of the usual kitchen waste, etc. Use vegetable and fruit scraps, coffee grounds (including paper filters), tea bags (remove the staple), eggshells (best dried and crushed first, then sprinkled over the surface), stale bread, houseplant trimmings. Chop up big chunks. Some people advise against citrus, onion, and garlic, others use them: try small quantities first. Be cautious with dairy products, meat and fish — small amounts chopped fine, well-dispersed and well-covered with bedding should be okay. Small broken chicken bones are okay, bigger bones won’t break down but shouldn’t cause problems either — they’ll be picked clean.

It’s best to collect food scraps in a small bucket with a lid and add them to the worm box every couple of days (or more often in hot weather — don’t let it go rotten). Bury them in the bedding in a corner of the box. Next time, bury the new scraps near the first scraps. You can have about nine burial sites in a 2x2ft box: by the time you’ve used the ninth one, you can go back to the first site again, the worms will have cleared it.

You’ll be surprised how much feed you can put in that box — the worms and micro-organisms reduce it more than you’d think possible.

The box will need emptying every 3-6 months.

Worms: These are not the usual big burrowing earthworms that live in garden soil. Composting worms are specialized surface dwellers (not deep burrowers). Two breeds are used in vermicomposting: Red Wigglers (Eisenia foetida) or Red Earthworms (Lumbricus rubellus). These are rarely found in soil and are adapted to the special conditions in rotting vegetation, compost and manure piles. Many garden centers now supply them, and in most countries they can be bought by mail order from worm farms. You’ll need around a 1,000 worms (1 lb) to start a worm box, maybe twice that if you want to process your garden wastes too — they breed very fast in the right conditions, but starting with more will give the system a good start.


Flies and smells: there shouldn’t be any, but sometimes it happens. Worm casts have a pleasant, earthy smell, like forest soil. If the worm bin starts to smell, there’s too much feed in it – more than the worms can process – you’ve overloaded the system. Stop feeding the worms, add more dry bedding, a little sprinkled lime, and stir the bin with a hand-fork. Repeat until the smell vanishes.

Fruit flies: (actually vinegar flies) can get into the box, but they do no harm. Lots of them mean too much feed — cut down the feeding rate and cover the surface with a damp newspaper.

Maggots: The bin can also have an influx of soldier fly maggots, up to an inch long (they’re a favourite with fishermen). Vinegar fly larvae are much smaller. Actually the maggots benefit the composting process, but if you don’t like them, add more bedding and lime and stir as above, or put a chunk of bread soaked in milk on the surface. In a couple of days it will be infested with larvae; take it out and get rid of it (give it to a fisherman or a chicken).


Use it like compost, for composting growing beds or preparing new beds, vermicompost generally goes about twice as far as ordinary (aerobic) compost, so use half as much. But each garden is different – some people have good results simply dumping large amounts of the stuff on top of their beds, others with very little.

Don’t let the vermicompost dry out before using it – it loses a lot of its value and resists wetting. If you store it, don’t use an airtight container. It will keep for a year or more.

You can also use vermicompost to make “compost tea” liquid fertilizer. Mix a couple tablespoons of vermicompost with a litre of water and let it stand for a day, shaking it occasionally, then sprinkle under the plants. One-litre drinks bottles make good sprinklers: simply drill a few small holes in the lid, point and squeeze.

For transplants, especially bare-root transplants, spray them with an even more dilute solution of “tea”, or stand them in it for awhile- it’ll help to prevent transplant shock.

Vermicompost also gives seedlings a really good start in life.

In pots and containers, don’t use pure vermicompost. About 25% of the growing mixture seems to be about ideal, but experiment depending on what you’re mixing it with.


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