By Elizabeth Spence
“Nobody likes me. Everybody hates me. I’m going down the garden to eat worms. . .” Anyone remember that childhood song?
Nobody can possibly hate the delightful David Flint (Lake Road) and Silvana Castillo (North Wallace). They don’t need to go down the garden to eat worms, so they farm them instead!
Jennifer and I visited David and Silvana at their respective abodes to find out what worm farming, or, more properly, “vermicomposting” is all about. Boy, did we learn a lot!! They have slightly different methods but the principles are the same.
Worm composting is basically keeping worms in a suitable environment, feeding them kitchen scraps and suchlike, and then collecting their castings (polite word for worm-poop) and the liquid that results from the whole procedure (leachate). Voila! You have magnificent compost and soil conditioner.
When we visited our amaryllis expert, Erica Lowe, she explained that she only ever puts worm castings on the soil around her bulbs, so it must be good.
As well as for top-dressing, you can use the castings to mix into your garden soil; you can use them as part of a potting mix, and you can make worm tea either out of the leachate or by soaking the solid castings in water.
Here is Silvana collecting her worm tea:
Science tells us that, “Castings contain 5 times the available nitrogen, 7 times the available potash, and 1½ times more calcium than found in good topsoil.”
They are sometimes called “the gardener’s secret weapon” because they boost microbiological activity in soil by adding bacteria and fungi as well as nutrients and other good things.
The first question we asked David and Silvana was whether we could use any old worms in this process. Could we dig up a few earthworms and throw them in with some apple corings and banana peels, for instance?
The answer in both cases was a resounding, “NO!”
“They have to be red wigglers!” they said.
What a delightful name! (Scientific name since 2003 is Eisenia fetida)
They are the absolute best worms when it comes to composting.
- they eat a lot – quickly;
- they reproduce – quickly;
- they stay near the surface (“epigeic”) as long as it is dark – unlike earthworms which burrow down and generally function a lot more slowly
- they are communal and don’t go off to find themselves individually as earthworms do.
Red wigglers can’t tolerate extremes in temperature, and certainly wouldn’t survive the winters outside here and so we found Silvana and her worm bin in her year-round greenhouse. She puts it outside in the shade in the summer. In this way it works year-round.
As you can see, it is very simple. The only thing you have to do to the bin initially is make ¼” holes everywhere, including in the cover, so that everything is very well aerated. The whole is elevated on pieces of wood so that the liquid can drip down into the tray underneath through screened holes in the bottom.
David’s system uses three totes, again with lots of ventilation. He uses soffit vents in holes drilled in the sides. There are also smaller holes drilled in the lid.
He also places pieces of wood at the bottom of the two lower bins to increase the air space when one bin is inserted on top of another:
His bins are also in his greenhouse now, but he keeps them in the basement over the winter. This means his system also works year-round.
They both use a tiered system although Silvana’s is not physically divided up as David’s is, apart from the separate juice-collecting tray at the bottom.
Silvana’s method is to start with a layer of food, then a layer of bedding, then, as the layers are gradually eaten up by the worms, she puts in another layer of food, another layer of bedding, and then another layer of food, another layer of bedding and so on and on. The worms automatically migrate to where the food is. The castings collect at the bottom of the bin.
The three-tier system David uses has the bottom bin for collecting the leachate or worm tea, the second bin for the first round of bedding, worms and food and where the castings collect. The top bin is for fresh bedding and food which the worms migrate to through the holes in the bottom of it as the worms eat their way through the contents of the second bin.
After a while, the second bin can be taken out, have the castings removed and then returned as the top bin, full of more bedding and food.
BEDDING
The most important thing you need for your worm farm to work well is layers of bedding. Silvana uses old leaves, seaweed and straw and puts it on top of food at the bottom of her bin.
David uses shredded paper.
Bedding is not only eaten by the worms, but is absolutely essential for creating air spaces and air movement in the whole system. It should be kept light and fluffy.
Many worm-farmers advise mixing a few different bedding materials together. Here are some of the things you can use:
FOOD
There are some things worms will eat, and there are some things that they won’t. Rather like me, really. Not that my diet consists of kitchen scraps, empty toilet rolls and grass clippings of course. Here’s their suggested menu:
It seems the worms absolutely LOVE shredded cardboard. Nobody’s quite sure why.
The things on the “bad” food list will all affect the worms’ physical functioning in one way or another, so they won’t eat them. As a result, these will just sit there, rot away and get very smelly.
In fact, both Silvana and David invited us to have a sniff, and, approaching cautiously, we perceived nothing but a lovely earthy smell. Not the rotting stench we were expecting and that we would have smelled if “bad” worm food had been sitting there untouched, or if conditions had been too wet, too dry, too hot or anaerobic – that is to say, without enough air.
It was a gentle, woodsy sort of smell. Rather like the scent of soil after a gentle rain that we examined in our article “Petrichor: Euphoria in the Garden”.
Did you know that you can buy earthworm-scented spray if the mood so takes you? Not red wiggler, it would seem, but near enough perhaps.
WORM ANATOMY
Studying the anatomy of worms is very interesting indeed and helps us understand how they function:
First of all, they don’t have teeth. Instead of biting their food, they push out their pharynx through the mouth and grab onto a little bit of food at a time and pull it in. They suck the food down into the crop and gizzard where it is ground up. It then goes on into the stomach and the intestine where it is further broken down by complex enzymatic processes. On the way, various chemicals are absorbed for energy to keep the worm going and the excess is finally excreted as compost.
This tells us a couple of things.
- The worm doesn’t immediately chow down on the fresh scraps it is given because they are too hard. It waits for microbes to start breaking things down a bit before they go at them. The food has to be at least partially decomposed and therefore soft enough so the worm can sink its pharynx into it.
- That means that you will have a head start on feeding if you cut up the food into smallish bits at the outset, since decomposition will proceed much more quickly and the food will be softer and more speedily available for the worms to eat.
- Just like birds – also toothless – worms have a crop and a gizzard which are used for grinding up food. This is why it is important to include some garden soil, sand or ground up eggshells in the mix. These gritty things do the job of teeth, but inside the digestive tract.
You will also see in the diagram that worms don’t have lungs. Oxygen diffuses from the air through the skin which has to be dampish and warm to function properly. Carbon dioxide is similarly released through the skin – a sort of exhaling.
This is why it is so important to have good air movement, enough moisture (about 70%) and an ambient temperature (about 15-25C) in the system, otherwise the worms will suffocate.
It pays to add water from time to time to ensure that all remains damp. Some people put damp newspaper, carboard or wool on top of everything like a sort of wet blanket. This really keeps the moisture in.
Worms don’t have eyes either, but they can detect light and dark through specialized receptor cells. If they are exposed to light for too long, they will become paralyzed and start drying out. That’s why they always seek the dark.
All this comes in very useful when collecting the compost. David takes a few handfuls of it out of the bin and places it in piles. The worms that have come along for the ride sense the light and immediately start burrowing to the bottom of the pile.
After a while he removes the worm-free compost and returns the worms themselves to the bins. Here he is working on it:
Silvana notes that when you want to separate the worms you can take advantage of the fact that they always go to where the food is. If you put wormy castings on one end of a large deep tray and put some of their food on the other, they will scuttle over to the food leaving worm-free castings for you to collect.
Both methods work with the inborn nature of worms. They’re not stressed out too badly. They are just doing what comes naturally.
After harvesting the compost, David and Silvana store it in buckets to be used as required.
USE
Vermicompost is easy to use in most applications. But some caution is advised: as the worms break down the organic matter they add enzymes and bacteria that really energize plant growth. The compost and the leachate are very rich indeed, so they need to be used sparingly
For top-dressing you can just sprinkle it lightly on the soil.
If you use it for your seedlings, you should use one part of it to ten parts potting mix. For older plants the ratio can be 2:10,
When you use the leachate – the worm tea – Silvana recommends that you dilute it 1:10 with water.
Just as in most things to do with gardening, the commercial world is putting its oar in. You can buy all sorts of things ready to go.
A complete worm farm kit:
Complete set of tools:
If you find you don’t have quite enough food at any particular time, fear not! Worm Chow is here!
Even a worm blanket to soak in water and put on top of everything
Worm castings.
Research shows that any pasteurising or sterilizing processes will kill off the benficial microrganisms which you will definitely find in fresh, home-made worm compost.
Silvana tells us that one of the disadvantages of non sterilized castings is that it will contain seeds. She writes:
There are a lot of seeds in the untreated castings, so be prepared when you start seeds to get companion plants! If you are working with a seed for the first time, and you don’t know what it looks like when young, don’t use worm castings as seed compost. Add them later when you know what you have.
(As an aside, a similar concern was voiced by Prof. David Boyle in part two of his article for us on microorganisms and fungi in the soil. He stated that it was most probable that the mycorhizae in bales of potting soil were dead owing to sterilization and bad storage conditions, and you were actually paying for something that wasn’t there.)
My favourite worm farming aid though, is this counter-top worm farm.
Just think! You don’t have to go anywhere to dispose of your kitchen scraps; you can spoon out compost for your houseplants without having to go outside, and you can release the worm tea through the spigot directly into a watering can. And you can do it at any time of year. How practical is that!
And, furthermore, when you are rustling up your favourite worm dish – you can steam, fry, bake or boil them – all you have to do is take them out of the bin, clean them well and prepare them. They apparently have a nutty taste and are a good source of protein, healthy fats, vitamins, and minerals. What more could you want in a food?
Silvana was our first Garden Neighbour on the website. David helps run the North Shore Garden Club.
They will supply you with worms and wonderful, wonderful advice as you start your new worm farm!
In fact, David has a GLUT of worms to give away at the moment (beginning of May, 2025). Deep-fried worms, anyone?
Copyright©2025 Elizabeth Spence