DIY Worm Farming
Vermiculture, or worm farming, is a great method for small- and medium-scale growers to improve soil quality. It's also a fantastic conversion of 'waste' food into very valuable materials - worm castings (poo) and tea (wee). I love teaching vermiculture workshops and find that kids in particular LOVE to learn about (and touch) worms. Worm farms are adaptable to many spaces, are portable, great to get kids interested in the garden, and save you money on soil inputs. I love them!
There are a few important tips I have to get you on your way and to help you maintain a healthy environment for you worms (they're living, breathing creatures who deserve good treatment, too!) which I'll share below. I also have a step-by-step guide below on how to build just one type of worm farm, should you be up for a little DIY project! Read on for more...
My homemade worm farm - note the tap down the bottom, and the height created bewteen each stackable layer by adding small pots inside each.
Where do I get my worms from?
Worms used in a worm farm are not your garden earthworms. There are many different species, a few of which are specific to worm farms or compost because they feed on dense scraps and procreate quickly. They're much smaller/thinner than earth worms and often striped. I recommend searching in your local area for a small-scale grower rather than buying commercial worm boxes from hardware stores, which are often transported and stored for long periods, often in the heat, and may provide you with hundreds of dead worms..! Poor buggers.
I found Geelong Worms in my neighbourhood, run by a local Permaculture educator Ernesto, who was much cheaper and more informative than the worm boxes! 500 worms is a minimum amount for a small farm, while 1000+ is recommended for anything more (speak to your provider about what's best for your size farm). If happy, they will breed quite rapidly.
What healthy worms need
To keep healthy, productive worms, you need to provide them with a space that's damp (but not soaking wet), dark (they're photophobic, or dislike light), cool, has bedding for laying eggs and resting, and plenty of food to munch through.
Shredded newspaper, unbleached paper or coconut fibre (coir peat) makes the best bedding - a few centimetres on the bottom of your top (feeding) layer dampened down regularly is perfect. They'll eat through this slowly too, so replace bedding as required.
A 'blanket' or covering on top is important to retain moisture and darkness, so keep this damp and in place at all times. You can simply use a folded 1/2 newspaper, hessian coffee sack, or buy a woollen 'worm blanket' if you like. Make sure you aren't adding synthetic materials as these will eventually end up in your garden, and worms.
Food for worms includes small chopped scraps of most foods, excluding the following:
- Citrus fruit
- Pet poo
- Meat and dairy
- Coffee grounds
- Avocado pips/very woody scraps
- Highly salty or fatty leftovers
On the flip side, worms love:
- Crushed egg shells (they have a gizzard like birds which requires grit to help crush their food)
- Tea leaves
- Juicer pulp
- Apple and banana scraps
- Chopped greens
Be aware that you can add too much food - if your worms can't get through their scraps in a few days, they will sit too long and go mouldy which invites other bugs and microbes into your worm farm. I can't tell you how much to add each feed as this depends on how many worms you have and how big your worm farm is, so this is up to you to observe over time!
Where do I place my worm farm?
To ensure it remains dark, cool, and practical for you to access, choose somewhere shaded near your house. Often the south side of a property is shaded 90% of the time. Keep in mind the change in sun angle from winter to summer, as during part of the year you might find it in full sun in the middle of the day. If your worm farm is right down the back of your property, it might be harder to access and check on regularly. Raising your farm off the ground a bit can also help to deter pests, as does adding a good lid, with a brick on top if it's easy to lift up.
On hot days, even without sun hot winds can be extremely drying in the garden. If I need to I'll cover my worm farm with a wet towel on these days to ensure my worms don't overheat and die.
I've bought/made my worm farm - how do I set it up?
Well done! OK, this part is important. You will need a reservoir and drain (tap or other drainage point) to collect the liquid, a layer (or multiple) to collect castings, and a layer to put bedding and food in. These two layers may be combined into one if you are to use something large like a bathtub (more on that below). In my farm pictured, I have three layers and will describe my setup as per this, as it's the most common system you'll find.
The bottom layer needs either a drainage hole or, ideally, a tap installed low down for easy liquid harvest (see below for more). The middle layers need small holes for worms, air and castings to get through, but not too big that your worms fall down into the liquid and drown (worms breathe through their skin, so swimming is suffocating!). The top layer is where the business happens - feeding, breeding and sleeping.
In your top layer, shred your chosen bedding (described above) up to a few centimetres deep and water down. On top, add your new worms. On top, add your damp blanket of choice and put the lid on. Leave in your chosen spot. In a week or so, add a couple of centimetres of chopped scraps and monitor how they eat - what they love, what they don't love, how fast/slow they get through it. Over time you should have eggs being laid in the bedding and soon baby worms everywhere.
When and how can I extract worm castings?
Worm castings, or vermicompost, are the result of your worms eating and processing your scraps, then excreting them as small black deposits that are amazing for your soil. They're full of microbes, hold moisture extremely well, and add organic matter to your soil. While they contain some nutrients, worm products are known more as a 'soil conditioner' because they're a great structural soil improver. To buy this stuff would cost you a mint, but you can make it (or the worms can for you) for free!
You can harvest castings when you have a few centimetres of obviously processed food scraps - it looks just like black, very moist (almost squidgy) soil. To avoid harvesting all your worms with it, here's how to do it:
- If you have a singular layer farm, such as an old bathtub, begin adding scraps only to one end of the tub for a couple of weeks. Worms will leave the processed castings and head for food, leaving you almost worm-free poo to harvest.
- If you have a multi-layer farm like mine (pictured), swap the top layer down a level and set up an empty top layer with fresh bedding, scraps, and blanket. As you have holes in the bottom of each layer, worms will migrate up over time and your second layer costings will be almost worm-free.
To use castings, spread them sparingly on outdoor pot-plants (under mulch) and garden beds, then water in well. You don't add this in large amounts like you might compost or manure. This is best done in Autumn and Spring.
What about worm tea?
Worm tea is the liquid that collects in the bottom of your worm farm and is a very concentrated brew of nutrients and microbes. I water down my worm farm about once a week with a litre or two from the watering can, which keeps everything damp and flushes through the castings, creating more tea to harvest. Then this is where your drain or tap comes in - harvest the liquid at least once a week (if it sits for a long time you may lose your microbe populations and can breed mosquitoes!). Dilute your worm tea in a watering can to the colour of weak black tea before adding to the garden - water pots, seedlings or advanced plants. Veggies, especially in planter boxes, love this stuff!
Do other critters in my worm farm cause harm?
You will definitely have a few bugs aside from worms find a home in your worm farm. I often have spiders, slugs and the occasional beetle in mine. I haven't generally noticed any problem caused by them! If you seem to really have an infestation of somethings - do some online research and you may find you just need to alter the moisture content or amount of scraps you're adding.
Our family creates far too many scraps to keep up with our worm farm. Help!
I can relate! Even though we're extremely good at using as much of our veggies as possible to minimise waste, we still have more scraps than our worms will eat in a household of four veggie-obsessed adults. So we also have a cold compost pile (see my blog post on composting here) and now, chooks! Compost and chook manure are so valuable in the garden, but not everyone is a gardener, so you may want to jump on the ShareWaste App to share your excess scraps with others in your suburb.
How to build a DIY worm farm - just one of many ways!
Before I start, let me first say: Whatever you can salvage second-hand, please do! I couldn't find what I needed when I made this worm farm, so bought everything new (but good quality to last a long time) and it didn't save me any money, or plastic from landfill. Sadly. If you can find containers or polystyrene boxes, use them!
Bottom layer with tap fixture and four small pots. I have not yet drilled rim air holes.
What you'll need
- A drill, a 1/8 inch drill bit and a circular drill bit the size of your tap fitting diameter
- At least three identical containers (read more below)
- A lid for the top container, or a piece of ply/opaque plastic to sit on top
- A tap with rubber washer or plumbing tape
- Plenty of old newspaper
- At least 500 vermiculture worms
- Eight small empty seedling pots, or something else durable and of a similar height
1) Decide how many layers you'd like. I chose three, the minimum - read above section for what happens in which layer. You may choose four or five! Each container needs to fit inside the next, so test this out before you buy/obtain them. I bought three black, UV-treated, thick tubs from Bunnings that are designed to fit inside each other. If your containers come with a lid, that's a great bonus.
2) In the bottom layer, drill a hole just above the bottom with your circular drill bit - this is where your worm wee tap will go. Follow instructions on the tap packaging for fitting (basically, you insert the tap and washer on the outside, and on the inside add a washer then the nut, and test for any leakage. Use some plumbing tape around the thread if your hole is a little big to help seal it).
Middle and top layers have holes drilled in bottom and just below the rim. I have not yet added small pots.
3) In the top and middle layers (NOT the bottom), drill 1/8 inch holes in the bottom (as pictured) and also a couple of inches below the top, all the way around the rim. Bin any microplastics that come off as you're drilling. In the bottom layer, drill holes around the rim as you did for the other layers, but NOT in the bottom of it. So all three layers should have rim air holes, but only the top and middle layers have holes in the bottom.
4) In the corners of the bottom and middle layers, place the small seedling pots (or whatever you choose to use). These are to stop your stackable containers from sliding all the way into each other - your worms need some space!
Wet shredded newspaper makes excellent bedding for worms in the top layer.
5) In the top layer, add bedding, worms and blanket as per my set-up instructions above. Stack all three (or more) layers together - bottom with tap; then middle with only holes; then top with bedding; then lid.
6) Place your worm farm in your chosen location (read above instructions on how to choose the best place for your worms) and, in a week or so, start adding scraps. Voila!
Our cheap, simple 'worm blanket' of wet newspaper, which we replace often as needed.
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