Build your own worm farm

G Magazine

Worms do a fantastic job of converting household scraps into nutrient-rich, eco-friendly plant food.

Worm farm

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It's easy to build a house for your very own colony of wriggly workers using materials you already have around the home, or can get and recycle for free.

What you'll need:

• Two watertight, durable boxes of equal size (polystyrofoam ones work best; ask your local fruit shop or supermarket)
• A lid to cover one of the boxes (either the lid it came with, or anything you have lying around that could be used as a covering)
• A small plastic drink bottle, with a lid
• Two bricks or brick-sized rocks
• Fine, non-biodegradable mesh
(like old fly-screen)
• An old jumper, hessian bag or other piece of material to cover the worms
• Shredded newspaper, old compost, leaves or soil
• 1,000 to 2,000 red or tiger compost worms (source these from friends
who have their own worm farms or buy from the local nursery)
• Durable, wide, waterproof tape
• A skewer or sharp object for piercing holes
• Blu-tack
• Food scraps

What to do:

1.) Choose the sturdiest and most waterproof-looking box to be your base box and cut a hole approximately 2.5 cm in diameter in one of its corners (enough for the neck of your bottle to fit snuggly through).

2.) Fit your bottle through the hole so its top and lid sticks out the corner of the box. This will be the worm farm's tap. Cut off the bottom of the bottle, so that about 2 cm remains in the box.

3.) Cut a few evenly spaced slits into the bit of the bottle inside the box only, so you can bend and tape the plastic down. It should fit flat against the walls of the box and be watertight. Mould blu-tack around the edges of the bottleneck on the outside of the box for extra water tightness.

4.) Pierce the base of the second box with small, skewer-sized holes about 1 cm apart and lay the mesh over the base, taping around the edges to hold in place. The holes will allow liquid to drain out of the box, while the mesh helps prevent worms from sneaking through the holes.

5.) Place a rock or brick in the base of your first box; if any worms fall through the holes and mesh of the top box this will provide an 'island' for them to climb on to avoid drowning.

6.) Rest the pierced box on top of the base box and tape the boxes together. Fill the top box with a 10 cm layer of shredded newspaper, old compost, leaves or soil. This will be the bedding for your worms.

7.) Introduce your worms to their new home by carefully spreading them over the bedding. Give them their first meal by adding a small amount of food scraps to the bed. Cover these with a small layer of extra bedding to avoid attracting vinegar flies.

8.) Cover the worms and bedding with an old cotton or woollen jumper, hessian bag or even a few sheets of newspaper — anything that will keep them in darkness (worms are sensitive to light) but still let water through. This layer will eventually need replacing because it will break down and be munched on by the worms.

9.) Find yourself a lid for the top of the worm farm. Whether it's lid that came with the top box or a makeshift one, it will be important to protect the worms and keep any vermin attracted to the food scraps from getting in. Punch the lid with small, skewer-sized holes about 1 cm apart to allow rainwater to penetrate the farm and keep the worms nice and moist. Rest a rock or brick on top as one last obstacle for vermin or pets trying to break in.

10.) Let your worms do their thing! When it's time to harvest the worm juice, which will be dripping down into the second box, just unscrew the bottle lid and drain it out. (Hint: wedging something under one corner to tilt the box will be a big help, encouraging the juice to drain towards the bottle.)

Worm food

Worms will eat most of your kitchen fruit and veg scraps, as well as crushed eggshells, coffee grinds, paper, shredded cardboard and dry leaves. There are, however, things you should avoid feeding them, including garlic, chilli and onions as well as acidic citrus fruit and peels. Steer clear too of dairy, meat and bones, seafood and oily food, as these can make the farm smelly, as well as attracting unwanted insects and pests.

Hungry workers

Worms have voracious appetites and can eat their own weight in food every few days. Top up their dinner plate about once a week after they have eaten most of their previous meal. Beware of overfeeding as uneaten food will make things quite stinky. Worms are also solid breeders - in good conditions they'll double their population every eight weeks. As they begin to breed, you'll need to feed them more often.

Worm farm maintenance

Your worm farm should be kept nicely moist - don't allow it to dry out, but don't let it get too soggy, either. If you're keeping it out in the open, natural rainfall will help, but you may want to provide some cover if you're facing days of torrential downpours. If you're keeping it in a shed or otherwise covered, remember to regularly add a good splash of water when you see things drying out. Also keep an eye on worm numbers. As your worms breed, things can become a little cramped. You can add another box to the top of your farm to accommodate the new additions or give them away to family and friends.

G TIP: Worm 'juice' is potent so be sure to dilute it at a rate of one part juice to 10 parts water before using on plants.